diff --git a/role_scripts/10/primary/start.sh b/role_scripts/10/primary/start.sh
index a98323b..ba14e81 100755
--- a/role_scripts/10/primary/start.sh
+++ b/role_scripts/10/primary/start.sh
@@ -369,7 +369,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 # ref: https://superuser.com/a/246841/985093
 cat /tmp/postgresql.conf $PGDATA/postgresql.conf >"/tmp/postgresql.conf.tmp" && mv "/tmp/postgresql.conf.tmp" "$PGDATA/postgresql.conf"
diff --git a/role_scripts/10/standby/ha_backup_job.sh b/role_scripts/10/standby/ha_backup_job.sh
index b6ee739..77dcf29 100755
--- a/role_scripts/10/standby/ha_backup_job.sh
+++ b/role_scripts/10/standby/ha_backup_job.sh
@@ -139,7 +139,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 if [[ "${SSL:-0}" == "ON" ]]; then
     echo "ssl = on" >>/tmp/postgresql.conf
diff --git a/role_scripts/10/standby/run.sh b/role_scripts/10/standby/run.sh
index 0320ae1..7974f11 100755
--- a/role_scripts/10/standby/run.sh
+++ b/role_scripts/10/standby/run.sh
@@ -203,7 +203,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 if [[ "${SSL:-0}" == "ON" ]]; then
     echo "ssl = on" >>/tmp/postgresql.conf
diff --git a/role_scripts/10/standby/warm_stanby.sh b/role_scripts/10/standby/warm_stanby.sh
index 70d6834..4c0c9ad 100755
--- a/role_scripts/10/standby/warm_stanby.sh
+++ b/role_scripts/10/standby/warm_stanby.sh
@@ -77,7 +77,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 if [[ "${SSL:-0}" == "ON" ]]; then
     echo "ssl = on" >>/tmp/postgresql.conf
diff --git a/role_scripts/11/primary/start.sh b/role_scripts/11/primary/start.sh
index f83706d..14bb1b2 100755
--- a/role_scripts/11/primary/start.sh
+++ b/role_scripts/11/primary/start.sh
@@ -432,7 +432,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 # ref: https://superuser.com/a/246841/985093
 cat /tmp/postgresql.conf $PGDATA/postgresql.conf >"/tmp/postgresql.conf.tmp" && mv "/tmp/postgresql.conf.tmp" "$PGDATA/postgresql.conf"
diff --git a/role_scripts/11/standby/ha_backup_job.sh b/role_scripts/11/standby/ha_backup_job.sh
index 15df5dc..6c5b256 100755
--- a/role_scripts/11/standby/ha_backup_job.sh
+++ b/role_scripts/11/standby/ha_backup_job.sh
@@ -138,7 +138,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 
 if [[ "${SSL:-0}" == "ON" ]]; then
diff --git a/role_scripts/11/standby/run.sh b/role_scripts/11/standby/run.sh
index 0fb80c2..821dd23 100755
--- a/role_scripts/11/standby/run.sh
+++ b/role_scripts/11/standby/run.sh
@@ -207,7 +207,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 if [[ "${SSL:-0}" == "ON" ]]; then
     echo "ssl = on" >>/tmp/postgresql.conf
diff --git a/role_scripts/11/standby/warm_stanby.sh b/role_scripts/11/standby/warm_stanby.sh
index c8e1c58..2aaa507 100755
--- a/role_scripts/11/standby/warm_stanby.sh
+++ b/role_scripts/11/standby/warm_stanby.sh
@@ -77,7 +77,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 
 if [[ "${SSL:-0}" == "ON" ]]; then
diff --git a/role_scripts/12/primary/start.sh b/role_scripts/12/primary/start.sh
index 085572b..99e5913 100755
--- a/role_scripts/12/primary/start.sh
+++ b/role_scripts/12/primary/start.sh
@@ -452,7 +452,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 
 # ref: https://superuser.com/a/246841/985093
diff --git a/role_scripts/12/standby/ha_backup_job.sh b/role_scripts/12/standby/ha_backup_job.sh
index d79e8d5..163f588 100755
--- a/role_scripts/12/standby/ha_backup_job.sh
+++ b/role_scripts/12/standby/ha_backup_job.sh
@@ -140,7 +140,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 
 if [[ "${SSL:-0}" == "ON" ]]; then
diff --git a/role_scripts/12/standby/run.sh b/role_scripts/12/standby/run.sh
index 85cc2cb..2364562 100755
--- a/role_scripts/12/standby/run.sh
+++ b/role_scripts/12/standby/run.sh
@@ -205,7 +205,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 if [[ "${SSL:-0}" == "ON" ]]; then
     echo "ssl = on" >>/tmp/postgresql.conf
diff --git a/role_scripts/12/standby/warm_stanby.sh b/role_scripts/12/standby/warm_stanby.sh
index d491780..4b6e0c9 100755
--- a/role_scripts/12/standby/warm_stanby.sh
+++ b/role_scripts/12/standby/warm_stanby.sh
@@ -86,7 +86,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 if [[ "${SSL:-0}" == "ON" ]]; then
     echo "ssl = on" >>/tmp/postgresql.conf
diff --git a/role_scripts/13/primary/start.sh b/role_scripts/13/primary/start.sh
index 3cadcce..387d814 100755
--- a/role_scripts/13/primary/start.sh
+++ b/role_scripts/13/primary/start.sh
@@ -482,7 +482,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 
 # ref: https://superuser.com/a/246841/985093
diff --git a/role_scripts/13/standby/ha_backup_job.sh b/role_scripts/13/standby/ha_backup_job.sh
index ee961bf..89dca66 100755
--- a/role_scripts/13/standby/ha_backup_job.sh
+++ b/role_scripts/13/standby/ha_backup_job.sh
@@ -140,7 +140,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 if [[ "${SSL:-0}" == "ON" ]]; then
     echo "ssl = on" >>/tmp/postgresql.conf
diff --git a/role_scripts/13/standby/run.sh b/role_scripts/13/standby/run.sh
index 7eee1d4..b3bd056 100755
--- a/role_scripts/13/standby/run.sh
+++ b/role_scripts/13/standby/run.sh
@@ -209,7 +209,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 
 if [[ "${SSL:-0}" == "ON" ]]; then
diff --git a/role_scripts/13/standby/warm_stanby.sh b/role_scripts/13/standby/warm_stanby.sh
index b39e1e8..c486898 100755
--- a/role_scripts/13/standby/warm_stanby.sh
+++ b/role_scripts/13/standby/warm_stanby.sh
@@ -80,7 +80,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 
 if [[ "${SSL:-0}" == "ON" ]]; then
diff --git a/role_scripts/14/primary/start.sh b/role_scripts/14/primary/start.sh
index 6015005..b61b096 100755
--- a/role_scripts/14/primary/start.sh
+++ b/role_scripts/14/primary/start.sh
@@ -487,7 +487,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 
 # ref: https://superuser.com/a/246841/985093
diff --git a/role_scripts/14/standby/ha_backup_job.sh b/role_scripts/14/standby/ha_backup_job.sh
index 444f001..17f2788 100755
--- a/role_scripts/14/standby/ha_backup_job.sh
+++ b/role_scripts/14/standby/ha_backup_job.sh
@@ -140,7 +140,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 if [[ "${SSL:-0}" == "ON" ]]; then
     echo "ssl = on" >>/tmp/postgresql.conf
diff --git a/role_scripts/14/standby/run.sh b/role_scripts/14/standby/run.sh
index 7db01e1..b6884a7 100755
--- a/role_scripts/14/standby/run.sh
+++ b/role_scripts/14/standby/run.sh
@@ -209,7 +209,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 
 if [[ "${SSL:-0}" == "ON" ]]; then
diff --git a/role_scripts/14/standby/warm_stanby.sh b/role_scripts/14/standby/warm_stanby.sh
index 928ec3d..c935f6e 100755
--- a/role_scripts/14/standby/warm_stanby.sh
+++ b/role_scripts/14/standby/warm_stanby.sh
@@ -80,7 +80,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 
 if [[ "${SSL:-0}" == "ON" ]]; then
diff --git a/role_scripts/15/primary/start.sh b/role_scripts/15/primary/start.sh
index 8896043..592d711 100755
--- a/role_scripts/15/primary/start.sh
+++ b/role_scripts/15/primary/start.sh
@@ -490,7 +490,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 
 # ref: https://superuser.com/a/246841/985093
diff --git a/role_scripts/15/standby/ha_backup_job.sh b/role_scripts/15/standby/ha_backup_job.sh
index ff53d0c..d546b8e 100755
--- a/role_scripts/15/standby/ha_backup_job.sh
+++ b/role_scripts/15/standby/ha_backup_job.sh
@@ -142,7 +142,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 if [[ "${SSL:-0}" == "ON" ]]; then
     echo "ssl = on" >>/tmp/postgresql.conf
diff --git a/role_scripts/15/standby/run.sh b/role_scripts/15/standby/run.sh
index 57c21cc..c780d80 100755
--- a/role_scripts/15/standby/run.sh
+++ b/role_scripts/15/standby/run.sh
@@ -208,7 +208,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 
 if [[ "${SSL:-0}" == "ON" ]]; then
diff --git a/role_scripts/15/standby/warm_stanby.sh b/role_scripts/15/standby/warm_stanby.sh
index efecb83..4e3a5b6 100755
--- a/role_scripts/15/standby/warm_stanby.sh
+++ b/role_scripts/15/standby/warm_stanby.sh
@@ -81,7 +81,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 
 if [[ "${SSL:-0}" == "ON" ]]; then
diff --git a/role_scripts/16/primary/start.sh b/role_scripts/16/primary/start.sh
index 9ecc8d9..c5012c5 100755
--- a/role_scripts/16/primary/start.sh
+++ b/role_scripts/16/primary/start.sh
@@ -468,7 +468,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 
 # ref: https://superuser.com/a/246841/985093
diff --git a/role_scripts/16/standby/ha_backup_job.sh b/role_scripts/16/standby/ha_backup_job.sh
index c654fcf..98091c5 100755
--- a/role_scripts/16/standby/ha_backup_job.sh
+++ b/role_scripts/16/standby/ha_backup_job.sh
@@ -142,7 +142,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 if [[ "${SSL:-0}" == "ON" ]]; then
     echo "ssl = on" >>/tmp/postgresql.conf
diff --git a/role_scripts/16/standby/run.sh b/role_scripts/16/standby/run.sh
index 63abf86..b5301cd 100755
--- a/role_scripts/16/standby/run.sh
+++ b/role_scripts/16/standby/run.sh
@@ -209,7 +209,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 
 if [[ "${SSL:-0}" == "ON" ]]; then
diff --git a/role_scripts/16/standby/warm_stanby.sh b/role_scripts/16/standby/warm_stanby.sh
index 75a59ea..18c76a2 100755
--- a/role_scripts/16/standby/warm_stanby.sh
+++ b/role_scripts/16/standby/warm_stanby.sh
@@ -81,7 +81,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 
 if [[ "${SSL:-0}" == "ON" ]]; then
diff --git a/role_scripts/17/primary/start.sh b/role_scripts/17/primary/start.sh
index 783406a..6c8bedb 100755
--- a/role_scripts/17/primary/start.sh
+++ b/role_scripts/17/primary/start.sh
@@ -478,7 +478,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 
 # ref: https://superuser.com/a/246841/985093
diff --git a/role_scripts/17/standby/ha_backup_job.sh b/role_scripts/17/standby/ha_backup_job.sh
index c654fcf..98091c5 100755
--- a/role_scripts/17/standby/ha_backup_job.sh
+++ b/role_scripts/17/standby/ha_backup_job.sh
@@ -142,7 +142,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 if [[ "${SSL:-0}" == "ON" ]]; then
     echo "ssl = on" >>/tmp/postgresql.conf
diff --git a/role_scripts/17/standby/run.sh b/role_scripts/17/standby/run.sh
index 8e518e4..60a3cac 100755
--- a/role_scripts/17/standby/run.sh
+++ b/role_scripts/17/standby/run.sh
@@ -209,7 +209,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 
 if [[ "${SSL:-0}" == "ON" ]]; then
diff --git a/role_scripts/17/standby/warm_stanby.sh b/role_scripts/17/standby/warm_stanby.sh
index 57e6e88..3352733 100755
--- a/role_scripts/17/standby/warm_stanby.sh
+++ b/role_scripts/17/standby/warm_stanby.sh
@@ -85,7 +85,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 
 if [[ "${SSL:-0}" == "ON" ]]; then
diff --git a/role_scripts/18/primary/start.sh b/role_scripts/18/primary/start.sh
index ab734d6..e3fb1c5 100755
--- a/role_scripts/18/primary/start.sh
+++ b/role_scripts/18/primary/start.sh
@@ -471,7 +471,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 
 # ref: https://superuser.com/a/246841/985093
diff --git a/role_scripts/18/standby/ha_backup_job.sh b/role_scripts/18/standby/ha_backup_job.sh
index c654fcf..98091c5 100755
--- a/role_scripts/18/standby/ha_backup_job.sh
+++ b/role_scripts/18/standby/ha_backup_job.sh
@@ -142,7 +142,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 if [[ "${SSL:-0}" == "ON" ]]; then
     echo "ssl = on" >>/tmp/postgresql.conf
diff --git a/role_scripts/18/standby/run.sh b/role_scripts/18/standby/run.sh
index 8e518e4..60a3cac 100755
--- a/role_scripts/18/standby/run.sh
+++ b/role_scripts/18/standby/run.sh
@@ -209,7 +209,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 
 if [[ "${SSL:-0}" == "ON" ]]; then
diff --git a/role_scripts/18/standby/warm_stanby.sh b/role_scripts/18/standby/warm_stanby.sh
index 57e6e88..3352733 100755
--- a/role_scripts/18/standby/warm_stanby.sh
+++ b/role_scripts/18/standby/warm_stanby.sh
@@ -85,7 +85,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 
 if [[ "${SSL:-0}" == "ON" ]]; then
diff --git a/role_scripts/9/primary/start.sh b/role_scripts/9/primary/start.sh
index 1d98613..0e2eaa9 100755
--- a/role_scripts/9/primary/start.sh
+++ b/role_scripts/9/primary/start.sh
@@ -364,7 +364,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 
 # ref: https://superuser.com/a/246841/985093
diff --git a/role_scripts/9/standby/ha_backup_job.sh b/role_scripts/9/standby/ha_backup_job.sh
index 6b2830c..106f101 100755
--- a/role_scripts/9/standby/ha_backup_job.sh
+++ b/role_scripts/9/standby/ha_backup_job.sh
@@ -139,7 +139,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 
 if [[ "${SSL:-0}" == "ON" ]]; then
diff --git a/role_scripts/9/standby/run.sh b/role_scripts/9/standby/run.sh
index fca2cd9..cc67f79 100755
--- a/role_scripts/9/standby/run.sh
+++ b/role_scripts/9/standby/run.sh
@@ -199,7 +199,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 
 if [[ "${SSL:-0}" == "ON" ]]; then
diff --git a/role_scripts/9/standby/warm_stanby.sh b/role_scripts/9/standby/warm_stanby.sh
index 779897a..4463a9b 100755
--- a/role_scripts/9/standby/warm_stanby.sh
+++ b/role_scripts/9/standby/warm_stanby.sh
@@ -78,7 +78,14 @@ if [[ "$STREAMING" == "synchronous" ]]; then
         done
         names=${names%,}
     fi
-    echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    # An empty list is a syntax error, not "no sync standbys" -- postgres refuses to start on
+    # 'FIRST 2 ()'. $names is empty whenever this pod is the only member it can see, e.g. a
+    # PITR restore at one replica. Empty means "wait for local flush only", so this is safe.
+    if [[ -z "${names:-}" ]]; then
+        echo "synchronous_standby_names = ''" >>/tmp/postgresql.conf
+    else
+        echo "synchronous_standby_names = '${SYNC_REPLICATION_MODE:-ANY} ${NUM_SYNC_REPLICAS:-1} ("$names")'" >>/tmp/postgresql.conf
+    fi
 fi
 
 if [[ "${SSL:-0}" == "ON" ]]; then