diff --git a/Common/make/ghdl.mk b/Common/make/ghdl.mk
index 92ba9a7..c5e5f97 100644
--- a/Common/make/ghdl.mk
+++ b/Common/make/ghdl.mk
@@ -56,7 +56,7 @@ all:  analyze
 
 $(WORK_DIR):
 	mkdir -p $@
-	cp $(TARGET).gtkw $(BUILD_DIR)
+	cp -u $(TARGET).gtkw $(BUILD_DIR)
 
 syntax: 
 	$(GHDL) -s $(GHDL_OPTS) $(SRCS)