diff --git a/src/UniTask/Assets/Plugins/UniTask/Editor/SplitterGUILayout.cs b/src/UniTask/Assets/Plugins/UniTask/Editor/SplitterGUILayout.cs
index dc0bd2a..4189133 100644
--- a/src/UniTask/Assets/Plugins/UniTask/Editor/SplitterGUILayout.cs
+++ b/src/UniTask/Assets/Plugins/UniTask/Editor/SplitterGUILayout.cs
@@ -1,5 +1,4 @@
-#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
+#pragma warning disable CS1591 // Missing XML comment for publicly visible type or member
 
 using System;
 using System.Linq;
@@ -61,4 +60,3 @@ namespace Cysharp.Threading.Tasks.Editor
     }
 }
 
-#endif
\ No newline at end of file
diff --git a/src/UniTask/Assets/Plugins/UniTask/Editor/UniTaskTrackerTreeView.cs b/src/UniTask/Assets/Plugins/UniTask/Editor/UniTaskTrackerTreeView.cs
index 377d0da..e7b6269 100644
--- a/src/UniTask/Assets/Plugins/UniTask/Editor/UniTaskTrackerTreeView.cs
+++ b/src/UniTask/Assets/Plugins/UniTask/Editor/UniTaskTrackerTreeView.cs
@@ -1,5 +1,4 @@
-#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
+#pragma warning disable CS1591 // Missing XML comment for publicly visible type or member
 
 using UnityEngine;
 using UnityEditor;
@@ -181,4 +180,3 @@ namespace Cysharp.Threading.Tasks.Editor
 
 }
 
-#endif
\ No newline at end of file
diff --git a/src/UniTask/Assets/Plugins/UniTask/Editor/UniTaskTrackerWindow.cs b/src/UniTask/Assets/Plugins/UniTask/Editor/UniTaskTrackerWindow.cs
index 08027a7..242ac6d 100644
--- a/src/UniTask/Assets/Plugins/UniTask/Editor/UniTaskTrackerWindow.cs
+++ b/src/UniTask/Assets/Plugins/UniTask/Editor/UniTaskTrackerWindow.cs
@@ -1,5 +1,4 @@
-#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
+#pragma warning disable CS1591 // Missing XML comment for publicly visible type or member
 
 using UnityEngine;
 using UnityEditor;
@@ -208,4 +207,3 @@ namespace Cysharp.Threading.Tasks.Editor
     }
 }
 
-#endif
\ No newline at end of file
diff --git a/src/UniTask/Assets/Plugins/UniTask/Internal/UnityEqualityComparer.cs b/src/UniTask/Assets/Plugins/UniTask/Internal/UnityEqualityComparer.cs
index 2fab3fe..906f3b6 100644
--- a/src/UniTask/Assets/Plugins/UniTask/Internal/UnityEqualityComparer.cs
+++ b/src/UniTask/Assets/Plugins/UniTask/Internal/UnityEqualityComparer.cs
@@ -1,8 +1,4 @@
-#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
-#endif
-
-using System;
+using System;
 using System.Collections.Generic;
 using UnityEngine;
 
diff --git a/src/UniTask/Assets/Plugins/UniTask/Triggers/AsyncAwakeTrigger.cs b/src/UniTask/Assets/Plugins/UniTask/Triggers/AsyncAwakeTrigger.cs
index 123c9f2..9c19914 100644
--- a/src/UniTask/Assets/Plugins/UniTask/Triggers/AsyncAwakeTrigger.cs
+++ b/src/UniTask/Assets/Plugins/UniTask/Triggers/AsyncAwakeTrigger.cs
@@ -1,5 +1,4 @@
-#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
+#pragma warning disable CS1591 // Missing XML comment for publicly visible type or member
 
 using System.Threading;
 using UnityEngine;
@@ -74,4 +73,3 @@ namespace Cysharp.Threading.Tasks.Triggers
     }
 }
 
-#endif
\ No newline at end of file
diff --git a/src/UniTask/Assets/Plugins/UniTask/Triggers/AsyncDestroyTrigger.cs b/src/UniTask/Assets/Plugins/UniTask/Triggers/AsyncDestroyTrigger.cs
index 7e9bd4a..cf522d5 100644
--- a/src/UniTask/Assets/Plugins/UniTask/Triggers/AsyncDestroyTrigger.cs
+++ b/src/UniTask/Assets/Plugins/UniTask/Triggers/AsyncDestroyTrigger.cs
@@ -1,5 +1,4 @@
-#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
+#pragma warning disable CS1591 // Missing XML comment for publicly visible type or member
 
 using System.Threading;
 using UnityEngine;
@@ -95,4 +94,3 @@ namespace Cysharp.Threading.Tasks.Triggers
     }
 }
 
-#endif
\ No newline at end of file
diff --git a/src/UniTask/Assets/Plugins/UniTask/Triggers/AsyncStartTrigger.cs b/src/UniTask/Assets/Plugins/UniTask/Triggers/AsyncStartTrigger.cs
index 4cc4766..94028c2 100644
--- a/src/UniTask/Assets/Plugins/UniTask/Triggers/AsyncStartTrigger.cs
+++ b/src/UniTask/Assets/Plugins/UniTask/Triggers/AsyncStartTrigger.cs
@@ -1,5 +1,4 @@
-#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
+#pragma warning disable CS1591 // Missing XML comment for publicly visible type or member
 
 using System.Threading;
 using UnityEngine;
@@ -84,4 +83,3 @@ namespace Cysharp.Threading.Tasks.Triggers
 
 }
 
-#endif
\ No newline at end of file
diff --git a/src/UniTask/Assets/Plugins/UniTask/Triggers/AsyncTriggerBase.cs b/src/UniTask/Assets/Plugins/UniTask/Triggers/AsyncTriggerBase.cs
index 7e87fbc..d959dca 100644
--- a/src/UniTask/Assets/Plugins/UniTask/Triggers/AsyncTriggerBase.cs
+++ b/src/UniTask/Assets/Plugins/UniTask/Triggers/AsyncTriggerBase.cs
@@ -1,5 +1,4 @@
-#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
+#pragma warning disable CS1591 // Missing XML comment for publicly visible type or member
 
 using System;
 using System.Collections.Generic;
@@ -382,4 +381,3 @@ namespace Cysharp.Threading.Tasks.Triggers
     }
 }
 
-#endif
\ No newline at end of file
diff --git a/src/UniTask/Assets/Plugins/UniTask/Triggers/AsyncTriggerExtensions.cs b/src/UniTask/Assets/Plugins/UniTask/Triggers/AsyncTriggerExtensions.cs
index a3ae68a..49bc5d2 100644
--- a/src/UniTask/Assets/Plugins/UniTask/Triggers/AsyncTriggerExtensions.cs
+++ b/src/UniTask/Assets/Plugins/UniTask/Triggers/AsyncTriggerExtensions.cs
@@ -1,5 +1,4 @@
-#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
+#pragma warning disable CS1591 // Missing XML comment for publicly visible type or member
 
 using System.Threading;
 using UnityEngine;
@@ -77,4 +76,3 @@ namespace Cysharp.Threading.Tasks.Triggers
     }
 }
 
-#endif
\ No newline at end of file
diff --git a/src/UniTask/Assets/Plugins/UniTask/UniTaskCompletionSource.cs b/src/UniTask/Assets/Plugins/UniTask/UniTaskCompletionSource.cs
index e114494..cba8dfa 100644
--- a/src/UniTask/Assets/Plugins/UniTask/UniTaskCompletionSource.cs
+++ b/src/UniTask/Assets/Plugins/UniTask/UniTaskCompletionSource.cs
@@ -259,7 +259,7 @@ namespace Cysharp.Threading.Tasks
         {
             if (token != version)
             {
-                throw new InvalidOperationException("token version is not matched.");
+                throw new InvalidOperationException("token version is not matched, can not await twice.");
             }
         }
     }
diff --git a/src/UniTask/Assets/Plugins/UniTask/UniTaskScheduler.cs b/src/UniTask/Assets/Plugins/UniTask/UniTaskScheduler.cs
index d047337..d725470 100644
--- a/src/UniTask/Assets/Plugins/UniTask/UniTaskScheduler.cs
+++ b/src/UniTask/Assets/Plugins/UniTask/UniTaskScheduler.cs
@@ -20,9 +20,9 @@ namespace Cysharp.Threading.Tasks
 #if UNITY_2018_3_OR_NEWER
 
         /// <summary>
-        /// Write log type when catch unobserved exception and not registered UnobservedTaskException. Default is Error.
+        /// Write log type when catch unobserved exception and not registered UnobservedTaskException. Default is Exception.
         /// </summary>
-        public static UnityEngine.LogType UnobservedExceptionWriteLogType = UnityEngine.LogType.Error;
+        public static UnityEngine.LogType UnobservedExceptionWriteLogType = UnityEngine.LogType.Exception;
 
         /// <summary>
         /// Dispatch exception event to Unity MainThread. Default is true.
diff --git a/src/UniTask/Assets/Scenes/ExceptionExamples.cs b/src/UniTask/Assets/Scenes/ExceptionExamples.cs
new file mode 100644
index 0000000..360f070
--- /dev/null
+++ b/src/UniTask/Assets/Scenes/ExceptionExamples.cs
@@ -0,0 +1,75 @@
+// Provided from: https://github.com/Cysharp/UniTask/issues/40
+
+using System;
+using System.Threading.Tasks;
+using Cysharp.Threading.Tasks;
+using UnityEngine;
+
+/// <summary>
+/// Example script for comparing how exceptions in unobserved tasks are handled between
+/// UniTask and normal tasks. This helps in verifying that unobserved exceptions are
+/// logged in a way that it useful to developers.
+/// </summary>
+public class ExceptionExamples : MonoBehaviour
+{
+    [SerializeField] private LogType _unobservedExceptionLogType = LogType.Exception;
+
+    private void Awake()
+    {
+        UniTaskScheduler.UnobservedExceptionWriteLogType = _unobservedExceptionLogType;
+    }
+
+    private void Start()
+    {
+        TaskScheduler.UnobservedTaskException += TaskScheduler_UnobservedTaskException;
+
+        ThrowFromAsyncVoid();
+        _ = ThrowFromTask();
+        _ = ThrowFromUniTask();
+
+        ThrowFromNonAsync();
+    }
+
+    private void TaskScheduler_UnobservedTaskException(object sender, UnobservedTaskExceptionEventArgs e)
+    {
+        UnityEngine.Debug.LogException(e.Exception);
+    }
+
+    private void ThrowFromNonAsync()
+    {
+        throw new Exception("Thrown from non-async function");
+    }
+
+    private async void ThrowFromAsyncVoid()
+    {
+        await ThrowInner();
+
+        async Task ThrowInner()
+        {
+            await UniTask.Yield();
+            throw new Exception("Thrown from `async void` function");
+        }
+    }
+
+    private async Task ThrowFromTask()
+    {
+        await ThrowInner();
+
+        async Task ThrowInner()
+        {
+            await UniTask.Yield();
+            throw new Exception("Thrown from `async Task` function");
+        }
+    }
+
+    private async UniTask ThrowFromUniTask()
+    {
+        await ThrowInner();
+
+        async UniTask ThrowInner()
+        {
+            await UniTask.Yield();
+            throw new Exception("Thrown from `async UniTask` function");
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/UniTask/Assets/Scenes/ExceptionExamples.cs.meta b/src/UniTask/Assets/Scenes/ExceptionExamples.cs.meta
new file mode 100644
index 0000000..4ebd641
--- /dev/null
+++ b/src/UniTask/Assets/Scenes/ExceptionExamples.cs.meta
@@ -0,0 +1,11 @@
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diff --git a/src/UniTask/Assets/Scenes/ExceptionExamples.unity b/src/UniTask/Assets/Scenes/ExceptionExamples.unity
new file mode 100644
index 0000000..bd45706
--- /dev/null
+++ b/src/UniTask/Assets/Scenes/ExceptionExamples.unity
@@ -0,0 +1,220 @@
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diff --git a/src/UniTask/Assets/Scenes/ExceptionExamples.unity.meta b/src/UniTask/Assets/Scenes/ExceptionExamples.unity.meta
new file mode 100644
index 0000000..ac078a0
--- /dev/null
+++ b/src/UniTask/Assets/Scenes/ExceptionExamples.unity.meta
@@ -0,0 +1,7 @@
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diff --git a/src/UniTask/Assets/Tests/Preserve.cs b/src/UniTask/Assets/Tests/Preserve.cs
new file mode 100644
index 0000000..d88b673
--- /dev/null
+++ b/src/UniTask/Assets/Tests/Preserve.cs
@@ -0,0 +1,47 @@
+using Cysharp.Threading.Tasks;
+using FluentAssertions;
+using NUnit.Framework;
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using UnityEngine.TestTools;
+
+namespace Cysharp.Threading.TasksTests
+{
+    public class Preserve
+    {
+        [UnityTest]
+        public IEnumerator AwaitTwice() => UniTask.ToCoroutine(async () =>
+        {
+            var delay = UniTask.DelayFrame(5);
+            await delay;
+
+            try
+            {
+                await delay;
+                Assert.Fail("should throw exception.");
+            }
+            catch (InvalidOperationException)
+            {
+
+            }
+        });
+
+        [UnityTest]
+        public IEnumerator PreserveAllowTwice() => UniTask.ToCoroutine(async () =>
+        {
+            var delay = UniTask.DelayFrame(5, PlayerLoopTiming.PostLateUpdate).Preserve();
+            var before = UnityEngine.Time.frameCount;
+            await delay;
+            var afterOne = UnityEngine.Time.frameCount;
+            await delay;
+            var afterTwo = UnityEngine.Time.frameCount;
+
+            (afterOne - before).Should().Be(5);
+            afterOne.Should().Be(afterTwo);
+        });
+    }
+}
diff --git a/src/UniTask/Assets/Tests/Preserve.cs.meta b/src/UniTask/Assets/Tests/Preserve.cs.meta
new file mode 100644
index 0000000..7cfee44
--- /dev/null
+++ b/src/UniTask/Assets/Tests/Preserve.cs.meta
@@ -0,0 +1,11 @@
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