diff --git a/flow/scripts/memories/extract_memories.tcl b/flow/scripts/memories/extract_memories.tcl
index 1bf12eff30..18e5c23717 100644
--- a/flow/scripts/memories/extract_memories.tcl
+++ b/flow/scripts/memories/extract_memories.tcl
@@ -4,14 +4,25 @@
 
 source $::env(SCRIPTS_DIR)/synth_preamble.tcl
 
+# This pass runs before gen_memories.py, so results/memories/blackboxes.txt
+# does not exist yet and there is nothing to blackbox: this is the pass
+# whose output that list is derived from. read_design_sources consults
+# auto_memories_blackboxes in every frontend branch, and that proc errors
+# out when the file is absent, so reading the sources with AUTO_MEMORIES
+# still set fails the step that has to run first. Clear it for this
+# process only; the guard keeps its strength for synthesis.
+set ::env(AUTO_MEMORIES) 0
+
 # Read all RTL sources using active frontend (all frontends)
 read_design_sources
 
 # Elaborate hierarchy
 hierarchy -top $::env(DESIGN_NAME)
 
-# Run process execution and memory collection
-proc
+# Run process execution and memory collection. `yosys proc` rather than
+# bare `proc`: yosys -import cannot shadow Tcl's proc keyword, so the
+# bare word would define a procedure instead of running the pass.
+yosys proc
 memory -nomap
 
 # Write netlist JSON containing inferred $mem_v2 primitives