diff --git a/.hgignore b/.hgignore
index efdc34c109..450a7e17be 100644
--- a/.hgignore
+++ b/.hgignore
@@ -19,6 +19,7 @@ doc/htmlgen
 src/Make.inc
 src/cmd/6a/6a
 src/cmd/?l/enam.c
+src/cmd/cc/y.output
 src/cmd/gc/builtin.c
 src/cmd/gc/mkbuiltin1
 src/cmd/gc/opnames.h