diff --git a/src/UniTask/Assets/Plugins/UniTask/Runtime/Linq/Merge.cs b/src/UniTask/Assets/Plugins/UniTask/Runtime/Linq/Merge.cs
index 86240a6..f129082 100644
--- a/src/UniTask/Assets/Plugins/UniTask/Runtime/Linq/Merge.cs
+++ b/src/UniTask/Assets/Plugins/UniTask/Runtime/Linq/Merge.cs
@@ -65,7 +65,7 @@ namespace Cysharp.Threading.Tasks.Linq
 
             readonly int length;
             readonly IUniTaskAsyncEnumerator<T>[] enumerators;
-            readonly int[] states;
+            readonly MergeSourceState[] states;
             readonly Queue<(T, Exception)> queuedResult = new Queue<(T, Exception)>();
             readonly CancellationToken cancellationToken;
 
@@ -75,7 +75,7 @@ namespace Cysharp.Threading.Tasks.Linq
             {
                 this.cancellationToken = cancellationToken;
                 length = sources.Length;
-                states = ArrayPool<int>.Shared.Rent(length);
+                states = ArrayPool<MergeSourceState>.Shared.Rent(length);
                 enumerators = ArrayPool<IUniTaskAsyncEnumerator<T>>.Shared.Rent(length);
                 for (var i = 0; i < length; i++)
                 {
@@ -112,18 +112,26 @@ namespace Cysharp.Threading.Tasks.Linq
 
                 for (var i = 0; i < length; i++)
                 {
-                    if (Interlocked.CompareExchange(ref states[i], (int)MergeSourceState.Running, (int)MergeSourceState.Pending) == (int)MergeSourceState.Pending)
+                    lock (queuedResult)
                     {
-                        var awaiter = enumerators[i].MoveNextAsync().GetAwaiter();
-                        if (awaiter.IsCompleted)
+                        if (states[i] == (int)MergeSourceState.Pending)
                         {
-                            GetResultAt(i, awaiter);
+                            states[i] = MergeSourceState.Running;
                         }
                         else
                         {
-                            awaiter.SourceOnCompleted(GetResultAtAction, StateTuple.Create(this, i, awaiter));
+                            continue;
                         }
                     }
+                    var awaiter = enumerators[i].MoveNextAsync().GetAwaiter();
+                    if (awaiter.IsCompleted)
+                    {
+                        GetResultAt(i, awaiter);
+                    }
+                    else
+                    {
+                        awaiter.SourceOnCompleted(GetResultAtAction, StateTuple.Create(this, i, awaiter));
+                    }
                 }
                 return new UniTask<bool>(this, completionSource.Version);
             }
@@ -135,7 +143,7 @@ namespace Cysharp.Threading.Tasks.Linq
                     await enumerators[i].DisposeAsync();
                 }
 
-                ArrayPool<int>.Shared.Return(states, true);
+                ArrayPool<MergeSourceState>.Shared.Return(states, true);
                 ArrayPool<IUniTaskAsyncEnumerator<T>>.Shared.Return(enumerators, true);
             }
 
@@ -153,7 +161,6 @@ namespace Cysharp.Threading.Tasks.Linq
                 try
                 {
                     hasNext = awaiter.GetResult();
-                    Interlocked.Exchange(ref states[index], (int)(hasNext ? MergeSourceState.Pending : MergeSourceState.Completed));
                 }
                 catch (Exception ex)
                 {
@@ -167,10 +174,11 @@ namespace Cysharp.Threading.Tasks.Linq
                     return;
                 }
 
-                var completedAll = IsCompletedAll();
-                if (hasNext || completedAll)
+                lock (queuedResult)
                 {
-                    lock (queuedResult)
+                    states[index] = hasNext ? MergeSourceState.Pending : MergeSourceState.Completed;
+                    var completedAll = !hasNext && IsCompletedAll();
+                    if (hasNext || completedAll)
                     {
                         if (completionSource.GetStatus(completionSource.Version).IsCompleted())
                         {
@@ -189,15 +197,12 @@ namespace Cysharp.Threading.Tasks.Linq
             {
                 for (var i = 0; i < length; i++)
                 {
-                    if (states[i] != (int)MergeSourceState.Completed)
+                    if (states[i] != MergeSourceState.Completed)
                     {
                         return false;
                     }
                 }
-                lock (queuedResult)
-                {
-                    return queuedResult.Count <= 0;
-                }
+                return true;
             }
         }
     }