diff --git a/src/sync/runtime_sema_test.go b/src/sync/runtime_sema_test.go
index 5b7dd3df3f0..a2382f46554 100644
--- a/src/sync/runtime_sema_test.go
+++ b/src/sync/runtime_sema_test.go
@@ -25,6 +25,9 @@ func BenchmarkSemaUncontended(b *testing.B) {
 }
 
 func benchmarkSema(b *testing.B, block, work bool) {
+	if b.N == 0 {
+		return
+	}
 	sem := uint32(0)
 	if block {
 		done := make(chan bool)