--- ./unix/Makefile.orig	2024-05-11 12:47:26.628830862 -0500
+++ ./unix/Makefile	2024-05-11 12:48:43.705832586 -0500
@@ -202,7 +202,7 @@
 	eval $(MAKE) $(MAKEF) zips `cat flags`
 
 generic_gcc:
-	$(MAKE) $(MAKEF) generic CC=gcc CPP="gcc -E"
+	$(MAKE) $(MAKEF) generic CC="gcc -std=gnu89" CPP="gcc -E"
 
 # AT&T 6300 PLUS (don't know yet how to allocate 64K bytes):
 att6300nodir: