diff --git a/src/UniTask/Assets/Plugins/UniTask/Runtime/UniTask.Delay.cs b/src/UniTask/Assets/Plugins/UniTask/Runtime/UniTask.Delay.cs
index 3105d9f..add6e70 100644
--- a/src/UniTask/Assets/Plugins/UniTask/Runtime/UniTask.Delay.cs
+++ b/src/UniTask/Assets/Plugins/UniTask/Runtime/UniTask.Delay.cs
@@ -108,7 +108,7 @@ namespace Cysharp.Threading.Tasks
 
 #if UNITY_EDITOR
             // force use Realtime.
-            if (!UnityEditor.EditorApplication.isPlaying)
+            if (PlayerLoopHelper.IsMainThread && !UnityEditor.EditorApplication.isPlaying)
             {
                 delayType = DelayType.Realtime;
             }