diff --git a/src/Microsoft.AspNetCore.Server.IISIntegration/Server/IISHttpContext.cs b/src/Microsoft.AspNetCore.Server.IISIntegration/Server/IISHttpContext.cs
index e7fe04d9d4..fb7f7cbb2f 100644
--- a/src/Microsoft.AspNetCore.Server.IISIntegration/Server/IISHttpContext.cs
+++ b/src/Microsoft.AspNetCore.Server.IISIntegration/Server/IISHttpContext.cs
@@ -332,9 +332,10 @@ namespace Microsoft.AspNetCore.Server.IISIntegration
         public unsafe void SendResponseHeaders(bool appCompleted)
         {
             // Verifies we have sent the statuscode before writing a header
-            var reasonPhrase = string.IsNullOrWhiteSpace(ReasonPhrase) ? ReasonPhrases.GetReasonPhrase(StatusCode) : ReasonPhrase;
-            var reasonPhraseBytes = Encoding.UTF8.GetBytes(reasonPhrase);
-
+            var reasonPhrase = string.IsNullOrEmpty(ReasonPhrase) ? ReasonPhrases.GetReasonPhrase(StatusCode) : ReasonPhrase;
+            var reasonPhraseBytes = new byte [reasonPhrase.Length + 1];
+            Encoding.ASCII.GetBytes(reasonPhrase, 0, reasonPhrase.Length, reasonPhraseBytes, 0);
+ 
             fixed (byte* pReasonPhrase = reasonPhraseBytes)
             {
                 Debug.Assert((IntPtr)pReasonPhrase != IntPtr.Zero);
diff --git a/test/IISIntegration.FunctionalTests/IISIntegration.FunctionalTests.csproj b/test/IISIntegration.FunctionalTests/IISIntegration.FunctionalTests.csproj
index 77f3646a70..c09eeee095 100644
--- a/test/IISIntegration.FunctionalTests/IISIntegration.FunctionalTests.csproj
+++ b/test/IISIntegration.FunctionalTests/IISIntegration.FunctionalTests.csproj
@@ -10,6 +10,7 @@
 
   <ItemGroup>
     <ProjectReference Include="..\..\src\Microsoft.AspNetCore.Server.IISIntegration\Microsoft.AspNetCore.Server.IISIntegration.csproj" />
+    <ProjectReference Include="..\IISTestSite\IISTestSite.csproj" />
   </ItemGroup>
 
   <ItemGroup>
diff --git a/test/IISIntegration.FunctionalTests/Inprocess/ResponseHeaderTests.cs b/test/IISIntegration.FunctionalTests/Inprocess/ResponseHeaderTests.cs
index 8cee6643a4..e54920e59d 100644
--- a/test/IISIntegration.FunctionalTests/Inprocess/ResponseHeaderTests.cs
+++ b/test/IISIntegration.FunctionalTests/Inprocess/ResponseHeaderTests.cs
@@ -40,7 +40,7 @@ namespace Microsoft.AspNetCore.Server.IISIntegration.FunctionalTests
             Assert.Equal("1", headerValues.First());
             Assert.Equal("2", headerValues.Last());
         }
-
+        
         [ConditionalFact]
         public async Task ErrorCodeIsSetForExceoptionDuringRequest()
         {
@@ -48,5 +48,17 @@ namespace Microsoft.AspNetCore.Server.IISIntegration.FunctionalTests
             Assert.Equal(HttpStatusCode.InternalServerError, response.StatusCode);
             Assert.Equal("Internal Server Error", response.ReasonPhrase);
         }
+
+        [ConditionalTheory]
+        [InlineData(1, "custom", "custom")]
+        [InlineData(500, "", "Internal Server Error")]
+        [InlineData(999, "", "")]
+        public async Task CustomErrorCodeWorks(int code, string reason, string expectedReason)
+        {
+            var response = await _fixture.Client.GetAsync($"SetCustomErorCode?code={code}&reason={reason}");
+            Assert.Equal((HttpStatusCode)code, response.StatusCode);
+            Assert.Equal(expectedReason, response.ReasonPhrase);
+            Assert.Equal("Body", await response.Content.ReadAsStringAsync());
+        }
     }
 }
diff --git a/test/IISTestSite/Startup.cs b/test/IISTestSite/Startup.cs
index a74524587a..28460cdaf5 100644
--- a/test/IISTestSite/Startup.cs
+++ b/test/IISTestSite/Startup.cs
@@ -218,6 +218,16 @@ namespace IISTestSite
             app.Run(ctx => { throw new Exception(); });
         }
 
+        private void SetCustomErorCode(IApplicationBuilder app)
+        {
+            app.Run(async ctx => {
+                    var feature = ctx.Features.Get<IHttpResponseFeature>();
+                    feature.ReasonPhrase = ctx.Request.Query["reason"];
+                    feature.StatusCode = int.Parse(ctx.Request.Query["code"]);
+                    await ctx.Response.WriteAsync("Body");
+                });
+        }
+
         private void HelloWorld(IApplicationBuilder app)
         {
             app.Run(async ctx =>