diff --git a/src/runtime/runtime2.go b/src/runtime/runtime2.go
index 96720846b2..e549b92aa6 100644
--- a/src/runtime/runtime2.go
+++ b/src/runtime/runtime2.go
@@ -523,9 +523,9 @@ const (
 
 // Values for m.freeWait.
 const (
-	freeMStack = 0 // M done, free stack and reference.
-	freeMRef   = 1 // M done, free reference.
-	freeMWait  = 2 // M still in use.
+	freeMStack = iota // M done, free stack and reference.
+	freeMRef          // M done, free reference.
+	freeMWait         // M still in use.
 )
 
 type m struct {