diff --git a/make/rules.mk b/make/rules.mk
index 63266255..9345e736 100644
--- a/make/rules.mk
+++ b/make/rules.mk
@@ -26,7 +26,7 @@ $(LIBDIR):
 #	$(RM) $*.o
 
 moc_%.cpp: %.h
-	$(MOC) -o $@ $<
+	$(MOC) $(filter -D% -I%,$(strip $(CPPFLAGS))) -o $@ $<
 
 rcc_%.cpp: %.qrc
 	$(RCC) -o $@ $<