diff --git a/src/UniTask/Assets/Tests/GenericsWhenAllAny.cs b/src/UniTask/Assets/Tests/GenericsWhenAllAny.cs
new file mode 100644
index 0000000..e9a3c90
--- /dev/null
+++ b/src/UniTask/Assets/Tests/GenericsWhenAllAny.cs
@@ -0,0 +1,165 @@
+#if CSHARP_7_OR_LATER || (UNITY_2018_3_OR_NEWER && (NET_STANDARD_2_0 || NET_4_6))
+#pragma warning disable CS1591 // Missing XML comment for publicly visible type or member
+
+using UnityEngine;
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using UnityEngine.UI;
+using UnityEngine.Scripting;
+using Cysharp.Threading.Tasks;
+using Unity.Collections;
+using System.Threading;
+using NUnit.Framework;
+using UnityEngine.TestTools;
+using FluentAssertions;
+
+namespace Cysharp.Threading.TasksTests
+{
+    public class GenericsWhenAllAny
+    {
+
+        [UnityTest]
+        public IEnumerator WhenAllT15() => UniTask.ToCoroutine(async () =>
+        {
+            var t01 = Tes<int>();
+            var t02 = Tes<int>();
+            var t03 = Tes<int>();
+            var t04 = Tes<int>();
+            var t05 = Tes<int>();
+            var t06 = Tes<int>();
+            var t07 = Tes<int>();
+            var t08 = Tes<int>();
+            var t09 = Tes<int>();
+            var t10 = Tes<int>();
+            var t11 = Tes<int>();
+            var t12 = Tes<int>();
+            var t13 = Tes<int>();
+            var t14 = Tes<int>();
+            var t15 = Tes<int>();
+
+            await UniTask.WhenAll(t01, t02, t03, t04, t05, t06, t07, t08, t09, t10, t11, t12, t13, t14, t15);
+        });
+
+        [UnityTest]
+        public IEnumerator WhenAllT01_Generics1() => UniTask.ToCoroutine(async () =>
+        {
+            var t01 = Tes<MyGenerics<int>>();
+
+            await UniTask.WhenAll(t01);
+        });
+
+        [UnityTest]
+        public IEnumerator WhenAllT02_Generics1() => UniTask.ToCoroutine(async () =>
+        {
+            var t01 = Tes<MyGenerics<int>>();
+            var t02 = Tes<MyGenerics<int>>();
+
+            await UniTask.WhenAll(t01, t02);
+        });
+
+        [UnityTest]
+        public IEnumerator WhenAllT03_Generics1() => UniTask.ToCoroutine(async () =>
+        {
+            var t01 = Tes<MyGenerics<int>>();
+            var t02 = Tes<MyGenerics<int>>();
+            var t03 = Tes<MyGenerics<int>>();
+
+            await UniTask.WhenAll(t01, t02, t03);
+        });
+
+        [UnityTest]
+        public IEnumerator WhenAllT04_Generics1() => UniTask.ToCoroutine(async () =>
+        {
+            var t01 = Tes<MyGenerics<int>>();
+            var t02 = Tes<MyGenerics<int>>();
+            var t03 = Tes<MyGenerics<int>>();
+            var t04 = Tes<MyGenerics<int>>();
+
+            await UniTask.WhenAll(t01, t02, t03, t04);
+        });
+
+        // will fail.
+
+        //[UnityTest]
+        //public IEnumerator WhenAllT05_Generics1() => UniTask.ToCoroutine(async () =>
+        //{
+        //    var t01 = Tes<MyGenerics<int>>();
+        //    var t02 = Tes<MyGenerics<int>>();
+        //    var t03 = Tes<MyGenerics<int>>();
+        //    var t04 = Tes<MyGenerics<int>>();
+        //    var t05 = Tes<MyGenerics<int>>();
+
+        //    await UniTask.WhenAll(t01, t02, t03, t04, t05);
+        //});
+
+        //[UnityTest]
+        //public IEnumerator WhenAllT06_Generics1() => UniTask.ToCoroutine(async () =>
+        //{
+        //    var t01 = Tes<MyGenerics<int>>();
+        //    var t02 = Tes<MyGenerics<int>>();
+        //    var t03 = Tes<MyGenerics<int>>();
+        //    var t04 = Tes<MyGenerics<int>>();
+        //    var t05 = Tes<MyGenerics<int>>();
+        //    var t06 = Tes<MyGenerics<int>>();
+
+        //    await UniTask.WhenAll(t01, t02, t03, t04, t05, t06);
+        //});
+
+        //[UnityTest]
+        //public IEnumerator WhenAllT07_Generics1() => UniTask.ToCoroutine(async () =>
+        //{
+        //    var t01 = Tes<MyGenerics<int>>();
+        //    var t02 = Tes<MyGenerics<int>>();
+        //    var t03 = Tes<MyGenerics<int>>();
+        //    var t04 = Tes<MyGenerics<int>>();
+        //    var t05 = Tes<MyGenerics<int>>();
+        //    var t06 = Tes<MyGenerics<int>>();
+        //    var t07 = Tes<MyGenerics<int>>();
+
+        //    await UniTask.WhenAll(t01, t02, t03, t04, t05, t06, t07);
+        //});
+
+        //[UnityTest]
+        //public IEnumerator WhenAllT15_Generics1() => UniTask.ToCoroutine(async () =>
+        //{
+        //    var t01 = Tes<MyGenerics<int>>();
+        //    var t02 = Tes<MyGenerics<int>>();
+        //    var t03 = Tes<MyGenerics<int>>();
+        //    var t04 = Tes<MyGenerics<int>>();
+        //    var t05 = Tes<MyGenerics<int>>();
+        //    var t06 = Tes<MyGenerics<int>>();
+        //    var t07 = Tes<MyGenerics<int>>();
+        //    var t08 = Tes<MyGenerics<int>>();
+        //    var t09 = Tes<MyGenerics<int>>();
+        //    var t10 = Tes<MyGenerics<int>>();
+        //    var t11 = Tes<MyGenerics<int>>();
+        //    var t12 = Tes<MyGenerics<int>>();
+        //    var t13 = Tes<MyGenerics<int>>();
+        //    var t14 = Tes<MyGenerics<int>>();
+        //    var t15 = Tes<MyGenerics<int>>();
+
+        //    await UniTask.WhenAll(t01, t02, t03, t04, t05, t06, t07, t08, t09, t10, t11, t12, t13, t14, t15);
+        //});
+
+        async UniTask<T> Tes<T>()
+        {
+            await UniTask.Yield();
+            return default;
+        }
+    }
+
+    public class MyGenerics<T>
+    {
+
+    }
+
+    public class MyGenerics2
+    {
+
+    }
+}
+
+#endif
\ No newline at end of file
diff --git a/src/UniTask/Assets/Tests/GenericsWhenAllAny.cs.meta b/src/UniTask/Assets/Tests/GenericsWhenAllAny.cs.meta
new file mode 100644
index 0000000..67ac5a6
--- /dev/null
+++ b/src/UniTask/Assets/Tests/GenericsWhenAllAny.cs.meta
@@ -0,0 +1,11 @@
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+  serializedVersion: 2
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