diff --git a/Makefile b/Makefile
index 3e73f3e68..53b6e6a22 100644
--- a/Makefile
+++ b/Makefile
@@ -120,6 +120,8 @@ endif
 
 REGRESS += drop
 
+PG_CFLAGS += -Wmissing-variable-declarations -Werror
+
 srcdir=`pwd`
 
 ag_regress_dir = $(srcdir)/regress