diff --git a/src/cmd/goyacc/Makefile b/src/cmd/goyacc/Makefile
index ac0f427cc5..87b3470c6a 100644
--- a/src/cmd/goyacc/Makefile
+++ b/src/cmd/goyacc/Makefile
@@ -15,3 +15,4 @@ units: goyacc units.y
 	$(GC) y.go
 	$(LD) -o units y.$O
 
+CLEANFILES += units y.go y.output