diff --git a/makefile b/makefile
index dad3826..456937b 100644
--- a/makefile
+++ b/makefile
@@ -30,7 +30,7 @@
 grammar:
 	mkdir -p $(BUILDPATH)/$(BOT)
 	flex -o $(OLEX) $(LEX)
-	bison -o $(OYACC) -d $(YACC)
+	bison -o $(OYACC) -d $(YACC) -Wcounterexamples
 clean:
 	rm -rf $(BUILDPATH)
 	rm -f $(LOCPATH)/debug/$(NAME)_debug