diff --git a/src/runtime/mgc.go b/src/runtime/mgc.go
index 64a2f3abef..0b996d8950 100644
--- a/src/runtime/mgc.go
+++ b/src/runtime/mgc.go
@@ -1129,8 +1129,6 @@ top:
 		// sitting in the per-P work caches.
 		// Flush and disable work caches.
 
-		gcMarkRootCheck()
-
 		// Disallow caching workbufs and indicate that we're in mark 2.
 		gcBlackenPromptly = true
 
@@ -1153,6 +1151,16 @@ top:
 			})
 		})
 
+		// Check that roots are marked. We should be able to
+		// do this before the forEachP, but based on issue
+		// #16083 there may be a (harmless) race where we can
+		// enter mark 2 while some workers are still scanning
+		// stacks. The forEachP ensures these scans are done.
+		//
+		// TODO(austin): Figure out the race and fix this
+		// properly.
+		gcMarkRootCheck()
+
 		// Now we can start up mark 2 workers.
 		atomic.Xaddint64(&gcController.dedicatedMarkWorkersNeeded, 0xffffffff)
 		atomic.Xaddint64(&gcController.fractionalMarkWorkersNeeded, 0xffffffff)