diff --git a/sql/net_serv.cc b/sql/net_serv.cc
index d3388bb2f62fe..5940318c6629c 100644
--- a/sql/net_serv.cc
+++ b/sql/net_serv.cc
@@ -986,6 +986,7 @@ my_real_read(NET *net, size_t *complen,
   size_t length;
   uint i,retry_count=0;
   ulong len=packet_error;
+  bool proxy_parsed= false;
   my_bool expect_error_packet __attribute__((unused))= 0;
   thr_alarm_t alarmed;
 #ifndef NO_ALARM
@@ -1253,16 +1254,21 @@ my_real_read(NET *net, size_t *complen,
 
 packets_out_of_order:
   {
-    switch (handle_proxy_header(net)) {
-    case ABORT:
+    if (!proxy_parsed)
+    {
+      switch (handle_proxy_header(net))
+      {
+      case ABORT:
         /* error happened, message is already written. */
         len= packet_error;
-        goto end; 
-    case RETRY:
+        goto end;
+      case RETRY:
+        proxy_parsed= true;
         goto retry;
-    case IGNORE:
+      case IGNORE:
         break;
-    }
+     }
+   }
 
     DBUG_PRINT("error",
                ("Packets out of order (Found: %d, expected %u)",
diff --git a/tests/mysql_client_test.c b/tests/mysql_client_test.c
index ef8f9c3d34a86..e0d818300ca59 100644
--- a/tests/mysql_client_test.c
+++ b/tests/mysql_client_test.c
@@ -20786,6 +20786,23 @@ static void test_proxy_header_limits()
   mysql_close(m);
 }
 
+/* Test that connection fails with multiple proxy headers (MDEV-40878) */
+static void test_proxy_header_multiple()
+{
+  MYSQL *m;
+  const char header[]= "PROXY TCP4 192.0.2.1 127.0.0.1 12345 3306\r\n"
+                       "PROXY TCP4 192.0.2.2 127.0.0.1 12346 3306\r\n";
+  myheader("test_proxy_header_multiple");
+
+  m = mysql_client_init(NULL);
+  DIE_UNLESS(m);
+  mysql_optionsv(m, MARIADB_OPT_PROXY_HEADER, header, sizeof(header)-1);
+
+  /* Connection should fail, second proxy header is interpreted as packet error */
+  DIE_UNLESS(mysql_real_connect(m, opt_host, "root", "", NULL, opt_port, opt_unix_socket, 0) == NULL);
+  mysql_close(m);
+}
+
 
 /*
   MDEV-37556 memory leak in proxy protocol for non-loopback
@@ -21095,6 +21112,7 @@ static void test_proxy_header()
   test_proxy_header_localhost();
   test_proxy_header_ignore();
   test_proxy_header_limits();
+  test_proxy_header_multiple();
   test_proxy_header_dbug_remote_connection();
   test_proxy_header_connect_errors_reset();
   test_proxy_header_proxy_host_connect_errors_reset();