diff --git a/Makefile b/Makefile
index 5fbaf59..27858f6 100644
--- a/Makefile
+++ b/Makefile
@@ -261,6 +261,11 @@ GETELTORITO := ./scripts/geteltorito
 # extract the DOS boot image from an iso (and fix it up so qemu can boot it)
 %.img: %.iso
 	$(GETELTORITO) -o $@ $<
+	if [ ! -e fix-hdd-image-`stat -c %s $@`.patch ]; then \
+            echo ERROR: need the correct fix-hdd-image patch; \
+            rm -f $@; \
+            false; \
+	fi
 	./scripts/hexpatch.pl --rm_on_fail $@ fix-hdd-image-`stat -c %s $@`.patch
 	$(call build_info,$<.bat)