diff --git a/src/cmd/prof/main.c b/src/cmd/prof/main.c
index f0acaf1c07..a2ae2e11e6 100644
--- a/src/cmd/prof/main.c
+++ b/src/cmd/prof/main.c
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// +build !plan9
+
 #include <u.h>
 #include <time.h>
 #include <libc.h>