diff --git a/src/runtime/os1_plan9.go b/src/runtime/os1_plan9.go
index 9581f0cb67d..aa9d67fe1e7 100644
--- a/src/runtime/os1_plan9.go
+++ b/src/runtime/os1_plan9.go
@@ -182,7 +182,7 @@ func exit(e int) {
 	} else {
 		// build error string
 		var tmp [32]byte
-		status = []byte(gostringnocopy(&itoa(tmp[:], uint64(e))[0]) + "\x00")
+		status = []byte(gostringnocopy(&itoa(tmp[:len(tmp)-1], uint64(e))[0]))
 	}
 	goexitsall(&status[0])
 	exits(&status[0])