diff --git a/src/runtime/proc1.go b/src/runtime/proc1.go
index 09cb775f0d..a5708162de 100644
--- a/src/runtime/proc1.go
+++ b/src/runtime/proc1.go
@@ -1538,7 +1538,7 @@ func resetspinning() {
 	if _g_.m.spinning {
 		_g_.m.spinning = false
 		nmspinning = xadd(&sched.nmspinning, -1)
-		if nmspinning < 0 {
+		if int32(nmspinning) < 0 {
 			throw("findrunnable: negative nmspinning")
 		}
 	} else {
diff --git a/src/runtime/runtime2.go b/src/runtime/runtime2.go
index 57cd869d88..fbd43d21da 100644
--- a/src/runtime/runtime2.go
+++ b/src/runtime/runtime2.go
@@ -429,7 +429,7 @@ type schedt struct {
 
 	pidle      puintptr // idle p's
 	npidle     uint32
-	nmspinning uint32
+	nmspinning uint32 // limited to [0, 2^31-1]
 
 	// Global runnable queue.
 	runqhead guintptr