diff --git a/Makefile.src.in b/Makefile.src.in
index 8c9e4a8f83..70a31d4b95 100644
--- a/Makefile.src.in
+++ b/Makefile.src.in
@@ -267,6 +267,6 @@ mrproper: clean
 	$(Q)rm -f rev.cpp
 
 %.o:
-	@echo '$(STAGE) No such source-file: $(@:%.o=%).[c|cpp|m|rc]'
+	@echo '$(STAGE) No such source-file: $(@:%.o=%).[c|cpp|mm|rc]'
 
 .PHONY: all mrproper depend clean FORCE