diff --git a/test/YetAnotherHttpHandler.Unity.Test/Assets/Tests/Compat/Assert.cs b/test/YetAnotherHttpHandler.Unity.Test/Assets/Tests/Compat/Assert.cs
index b410439..f5e5bf2 100644
--- a/test/YetAnotherHttpHandler.Unity.Test/Assets/Tests/Compat/Assert.cs
+++ b/test/YetAnotherHttpHandler.Unity.Test/Assets/Tests/Compat/Assert.cs
@@ -30,6 +30,9 @@ public static T IsAssignableFrom<T>(object actual)
         return (T)actual;
     }
 
+    public static void Contains(string expected, string actual)
+        => NUnit.Framework.Assert.That(() => actual.Contains(expected));
+
     public static T IsType<T>(object actual)
     {
         NUnit.Framework.Assert.True(actual.GetType() == typeof(T), $"Expected: {typeof(T)}\nActual: {actual.GetType()}");
diff --git a/test/YetAnotherHttpHandler.Unity.Test/Assets/Tests/Http1Test.cs b/test/YetAnotherHttpHandler.Unity.Test/Assets/Tests/Http1Test.cs
index f591d8c..3c585c8 100644
--- a/test/YetAnotherHttpHandler.Unity.Test/Assets/Tests/Http1Test.cs
+++ b/test/YetAnotherHttpHandler.Unity.Test/Assets/Tests/Http1Test.cs
@@ -22,6 +22,23 @@ public async Task FailedToConnect()
 
         // Assert
         Assert.IsType<HttpRequestException>(ex);
+        Assert.Contains("(Connect): dns error", ex.Message);
+    }
+
+    [Fact]
+    public async Task FailedToConnect_VersionMismatch()
+    {
+        // Arrange
+        using var httpHandler = new Cysharp.Net.Http.YetAnotherHttpHandler() { Http2Only = true };
+        var httpClient = new HttpClient(httpHandler);
+        await using var server = await LaunchServerAsync<TestServerForHttp1AndHttp2>(TestWebAppServerListenMode.InsecureHttp1Only);
+
+        // Act
+        var ex = await Record.ExceptionAsync(async () => (await httpClient.GetAsync($"{server.BaseUri}/")).EnsureSuccessStatusCode());
+
+        // Assert
+        Assert.IsType<HttpRequestException>(ex);
+        Assert.Contains("'HTTP_1_1_REQUIRED' (0xd)", ex.Message);
     }
 
     [Fact]
diff --git a/test/YetAnotherHttpHandler.Unity.Test/Assets/Tests/Http2ClearTextTest.cs b/test/YetAnotherHttpHandler.Unity.Test/Assets/Tests/Http2ClearTextTest.cs
index fb624a8..375c0fd 100644
--- a/test/YetAnotherHttpHandler.Unity.Test/Assets/Tests/Http2ClearTextTest.cs
+++ b/test/YetAnotherHttpHandler.Unity.Test/Assets/Tests/Http2ClearTextTest.cs
@@ -7,6 +7,7 @@
 using System.Threading.Tasks;
 using System.Net.Http.Headers;
 
+using Fact = NUnit.Framework.TestAttribute;
 using ConditionalFact = NUnit.Framework.TestAttribute;
 using Grpc.Core;
 using System.IO;
@@ -17,6 +18,21 @@
 
 public class Http2ClearTextTest : YahaUnityTestBase
 {
+    [Fact]
+    public async Task FailedToConnect_VersionMismatch()
+    {
+        // Arrange
+        using var httpHandler = new Cysharp.Net.Http.YetAnotherHttpHandler() { Http2Only = false };
+        var httpClient = new HttpClient(httpHandler);
+        await using var server = await LaunchServerAsync<TestServerForHttp1AndHttp2>();
+
+        // Act
+        var ex = await Record.ExceptionAsync(async () => (await httpClient.GetAsync($"{server.BaseUri}/")).EnsureSuccessStatusCode());
+
+        // Assert
+        Assert.IsType<HttpRequestException>(ex);
+    }
+
     [ConditionalFact]
     public async Task Get_Ok()
     {