diff --git a/src/Microsoft.AspNet.Mvc.Core/ActionResults/ObjectResult.cs b/src/Microsoft.AspNet.Mvc.Core/ActionResults/ObjectResult.cs
index 69fd10e367..a6a47e9d81 100644
--- a/src/Microsoft.AspNet.Mvc.Core/ActionResults/ObjectResult.cs
+++ b/src/Microsoft.AspNet.Mvc.Core/ActionResults/ObjectResult.cs
@@ -94,8 +94,9 @@ namespace Microsoft.AspNet.Mvc
                         foreach (var formatter in formatters)
                         {
                             var supportedContentTypes = formatter.GetSupportedContentTypes(
-                                                                        GetObjectType(formatterContext),
-                                                                        contentType: null);
+                                                                         formatterContext.DeclaredType,
+                                                                         formatterContext.Object?.GetType(),
+                                                                         contentType: null);
 
                             if (formatter.CanWriteResult(formatterContext, supportedContentTypes?.FirstOrDefault()))
                             {
@@ -218,18 +219,5 @@ namespace Microsoft.AspNet.Mvc
 
             return formatters;
         }
-
-        private Type GetObjectType([NotNull] OutputFormatterContext context)
-        {
-            if (context.DeclaredType == null || context.DeclaredType == typeof(object))
-            {
-                if (context.Object != null)
-                {
-                    return context.Object.GetType();
-                }
-            }
-
-            return context.DeclaredType;
-        }
     }
 }
\ No newline at end of file
diff --git a/src/Microsoft.AspNet.Mvc.Core/Formatters/IOutputFormatter.cs b/src/Microsoft.AspNet.Mvc.Core/Formatters/IOutputFormatter.cs
index 5a43ecd975..9d04e598b7 100644
--- a/src/Microsoft.AspNet.Mvc.Core/Formatters/IOutputFormatter.cs
+++ b/src/Microsoft.AspNet.Mvc.Core/Formatters/IOutputFormatter.cs
@@ -20,12 +20,13 @@ namespace Microsoft.AspNet.Mvc
     {
         /// <summary>
         /// Gets a filtered list of content types which are supported by this formatter 
-        /// for the <paramref name="dataType"/> and <paramref name="contentType"/>.
+        /// for the <paramref name="declaredType"/> and <paramref name="contentType"/>.
         /// </summary>
-        /// <param name="dataType">Type for which the supported content types are desired.</param>
+        /// <param name="declaredType">The declared type for which the supported content types are desired.</param>
+        /// <param name="instanceType">The runtime type for which the supported content types are desired.</param>
         /// <param name="contentType">Content type for which the supported content types are desired.</param>
-        /// <returns>Content types which can are supported by this formatter.</returns>
-        IReadOnlyList<MediaTypeHeaderValue> GetSupportedContentTypes(Type dataType, MediaTypeHeaderValue contentType);
+        /// <returns>Content types which are supported by this formatter.</returns>
+        IReadOnlyList<MediaTypeHeaderValue> GetSupportedContentTypes(Type declaredType, Type instanceType, MediaTypeHeaderValue contentType);
 
         /// <summary>
         /// Determines whether this <see cref="IOutputFormatter"/> can serialize
diff --git a/src/Microsoft.AspNet.Mvc.Core/Formatters/NoContentFormatter.cs b/src/Microsoft.AspNet.Mvc.Core/Formatters/NoContentFormatter.cs
index 9ba33c9d44..5d2ab6e833 100644
--- a/src/Microsoft.AspNet.Mvc.Core/Formatters/NoContentFormatter.cs
+++ b/src/Microsoft.AspNet.Mvc.Core/Formatters/NoContentFormatter.cs
@@ -21,7 +21,7 @@ namespace Microsoft.AspNet.Mvc
             return context.Object == null;
         }
 
-        public IReadOnlyList<MediaTypeHeaderValue> GetSupportedContentTypes(Type dataType, MediaTypeHeaderValue contentType)
+        public IReadOnlyList<MediaTypeHeaderValue> GetSupportedContentTypes(Type declaredType, Type runtimeType, MediaTypeHeaderValue contentType)
         {
             return null;
         }
diff --git a/src/Microsoft.AspNet.Mvc.Core/Formatters/OutputFormatter.cs b/src/Microsoft.AspNet.Mvc.Core/Formatters/OutputFormatter.cs
index 438f21e099..4237214a2d 100644
--- a/src/Microsoft.AspNet.Mvc.Core/Formatters/OutputFormatter.cs
+++ b/src/Microsoft.AspNet.Mvc.Core/Formatters/OutputFormatter.cs
@@ -40,7 +40,7 @@ namespace Microsoft.AspNet.Mvc
         public IList<MediaTypeHeaderValue> SupportedMediaTypes { get; private set; }
 
         /// <inheritdoc />
-        public virtual IReadOnlyList<MediaTypeHeaderValue> GetSupportedContentTypes(Type dataType, MediaTypeHeaderValue contentType)
+        public virtual IReadOnlyList<MediaTypeHeaderValue> GetSupportedContentTypes(Type declaredType, Type runtimeType, MediaTypeHeaderValue contentType)
         {
             var mediaTypes = new List<MediaTypeHeaderValue>();
 
diff --git a/test/Microsoft.AspNet.Mvc.Core.Test/ActionResults/ObjectResultTests.cs b/test/Microsoft.AspNet.Mvc.Core.Test/ActionResults/ObjectResultTests.cs
index bfee0fccfd..43d21f8f17 100644
--- a/test/Microsoft.AspNet.Mvc.Core.Test/ActionResults/ObjectResultTests.cs
+++ b/test/Microsoft.AspNet.Mvc.Core.Test/ActionResults/ObjectResultTests.cs
@@ -550,7 +550,8 @@ namespace Microsoft.AspNet.Mvc.Core.Test.ActionResults
                 return false;
             }
 
-            public IReadOnlyList<MediaTypeHeaderValue> GetSupportedContentTypes(Type dataType,
+            public IReadOnlyList<MediaTypeHeaderValue> GetSupportedContentTypes(Type declaredType,
+                                                                                Type runtimeType,
                                                                                 MediaTypeHeaderValue contentType)
             {
                 return null;
diff --git a/test/Microsoft.AspNet.Mvc.Core.Test/JsonResultTest.cs b/test/Microsoft.AspNet.Mvc.Core.Test/JsonResultTest.cs
index 28931ecaa6..57666f66dc 100644
--- a/test/Microsoft.AspNet.Mvc.Core.Test/JsonResultTest.cs
+++ b/test/Microsoft.AspNet.Mvc.Core.Test/JsonResultTest.cs
@@ -118,7 +118,8 @@ namespace Microsoft.AspNet.Mvc
                 return true;
             }
 
-            public IReadOnlyList<MediaTypeHeaderValue> GetSupportedContentTypes(Type dataType, 
+            public IReadOnlyList<MediaTypeHeaderValue> GetSupportedContentTypes(Type declaredType,
+                                                                                Type runtimeType,
                                                                                 MediaTypeHeaderValue contentType)
             {
                 return null;
diff --git a/test/Microsoft.AspNet.Mvc.Core.Test/OptionDescriptors/OutputFormatterDescriptorTest.cs b/test/Microsoft.AspNet.Mvc.Core.Test/OptionDescriptors/OutputFormatterDescriptorTest.cs
index 78cff7970d..0a4affb277 100644
--- a/test/Microsoft.AspNet.Mvc.Core.Test/OptionDescriptors/OutputFormatterDescriptorTest.cs
+++ b/test/Microsoft.AspNet.Mvc.Core.Test/OptionDescriptors/OutputFormatterDescriptorTest.cs
@@ -62,7 +62,8 @@ namespace Microsoft.AspNet.Mvc.Core
                 throw new NotImplementedException();
             }
 
-            public IReadOnlyList<MediaTypeHeaderValue> GetSupportedContentTypes(Type dataType,
+            public IReadOnlyList<MediaTypeHeaderValue> GetSupportedContentTypes(Type declaredType,
+                                                                                Type runtimeType,
                                                                                 MediaTypeHeaderValue contentType)
             {
                 return null;
diff --git a/test/WebSites/ConnegWebSite/Controllers/FallbackOnTypeBasedMatchController.cs b/test/WebSites/ConnegWebSite/Controllers/FallbackOnTypeBasedMatchController.cs
index b200d7de49..8e233e0ce5 100644
--- a/test/WebSites/ConnegWebSite/Controllers/FallbackOnTypeBasedMatchController.cs
+++ b/test/WebSites/ConnegWebSite/Controllers/FallbackOnTypeBasedMatchController.cs
@@ -74,7 +74,7 @@ namespace ConnegWebsite
                 return contentType == null;
             }
 
-            public IReadOnlyList<MediaTypeHeaderValue> GetSupportedContentTypes(Type dataType, MediaTypeHeaderValue contentType)
+            public IReadOnlyList<MediaTypeHeaderValue> GetSupportedContentTypes(Type declaredType, Type runtimeType, MediaTypeHeaderValue contentType)
             {
                 return null;
             }