diff --git a/src/Microsoft.AspNet.Mvc.ModelBinding/Internal/TypeExtensions.cs b/src/Microsoft.AspNet.Mvc.ModelBinding/Internal/TypeExtensions.cs
index b4e18196e1..117d413f0f 100644
--- a/src/Microsoft.AspNet.Mvc.ModelBinding/Internal/TypeExtensions.cs
+++ b/src/Microsoft.AspNet.Mvc.ModelBinding/Internal/TypeExtensions.cs
@@ -5,23 +5,23 @@ namespace Microsoft.AspNet.Mvc.ModelBinding.Internal
 {
     public static class TypeExtensions
     {
-        public static bool IsCompatibleWith(this Type type, object value)
+        public static bool IsCompatibleWith([NotNull] this Type type, object value)
         {
             return (value == null && AllowsNullValue(type)) ||
-                   type.GetTypeInfo().IsAssignableFrom(value.GetType().GetTypeInfo());
+                (value != null && type.GetTypeInfo().IsAssignableFrom(value.GetType().GetTypeInfo()));
         }
 
-        public static bool IsNullableValueType(this Type type)
+        public static bool IsNullableValueType([NotNull] this Type type)
         {
             return Nullable.GetUnderlyingType(type) != null;
         }
 
-        public static bool AllowsNullValue(this Type type)
+        public static bool AllowsNullValue([NotNull] this Type type)
         {
             return (!type.GetTypeInfo().IsValueType || IsNullableValueType(type));
         }
 
-        public static bool HasStringConverter(this Type type)
+        public static bool HasStringConverter([NotNull] this Type type)
         {
             // TODO: This depends on TypeConverter which does not exist in the CoreCLR.
             // return TypeDescriptor.GetConverter(type).CanConvertFrom(typeof(string));
@@ -38,7 +38,7 @@ namespace Microsoft.AspNet.Mvc.ModelBinding.Internal
             return false;
         }
 
-        public static Type[] GetTypeArgumentsIfMatch(Type closedType, Type matchingOpenType)
+        public static Type[] GetTypeArgumentsIfMatch([NotNull] Type closedType, Type matchingOpenType)
         {
             TypeInfo closedTypeInfo = closedType.GetTypeInfo();
             if (!closedTypeInfo.IsGenericType)
diff --git a/test/Microsoft.AspNet.Mvc.ModelBinding.Test/Binders/ComplexModelDtoResultTest.cs b/test/Microsoft.AspNet.Mvc.ModelBinding.Test/Binders/ComplexModelDtoResultTest.cs
index 7c7c78ee8a..d8d0cf0e53 100644
--- a/test/Microsoft.AspNet.Mvc.ModelBinding.Test/Binders/ComplexModelDtoResultTest.cs
+++ b/test/Microsoft.AspNet.Mvc.ModelBinding.Test/Binders/ComplexModelDtoResultTest.cs
@@ -4,14 +4,15 @@ namespace Microsoft.AspNet.Mvc.ModelBinding.Test
 {
     public class ComplexModelDtoResultTest
     {
-        [Fact]
-        public void Constructor_ThrowsIfValidationNodeIsNull()
-        {
-            // Act & assert
-            ExceptionAssert.ThrowsArgumentNull(
-                () => new ComplexModelDtoResult("some string"),
-                "validationNode");
-        }
+        // TODO: Validation
+        ////[Fact]
+        ////public void Constructor_ThrowsIfValidationNodeIsNull()
+        ////{
+        ////    // Act & assert
+        ////    ExceptionAssert.ThrowsArgumentNull(
+        ////        () => new ComplexModelDtoResult("some string"),
+        ////        "validationNode");
+        ////}
 
         // TODO: Validation
         //[Fact]
diff --git a/test/Microsoft.AspNet.Mvc.ModelBinding.Test/Binders/TypeConverterModelBinderTest.cs b/test/Microsoft.AspNet.Mvc.ModelBinding.Test/Binders/TypeConverterModelBinderTest.cs
index 1802148a18..68d42fbea7 100644
--- a/test/Microsoft.AspNet.Mvc.ModelBinding.Test/Binders/TypeConverterModelBinderTest.cs
+++ b/test/Microsoft.AspNet.Mvc.ModelBinding.Test/Binders/TypeConverterModelBinderTest.cs
@@ -24,30 +24,11 @@ namespace Microsoft.AspNet.Mvc.ModelBinding.Test
             // Act
             bool retVal = binder.BindModel(bindingContext);
 
-            // Assert
-            Assert.False(retVal);
-            Assert.Equal("The value 'not an integer' is not valid for Int32.", bindingContext.ModelState["theModelName"].Errors[0].ErrorMessage);
-        }
-
-        [Fact]
-        public void BindModel_Error_FormatExceptionsTurnedIntoStringsInModelState_ErrorNotAddedIfCallbackReturnsNull()
-        {
-            // Arrange
-            ModelBindingContext bindingContext = GetBindingContext(typeof(int));
-            bindingContext.ValueProvider = new SimpleHttpValueProvider
-            {
-                { "theModelName", "not an integer" }
-            };
-
-            TypeConverterModelBinder binder = new TypeConverterModelBinder();
-
-            // Act
-            bool retVal = binder.BindModel(bindingContext);
-
             // Assert
             Assert.False(retVal);
             Assert.Null(bindingContext.Model);
-            Assert.True(bindingContext.ModelState.IsValid);
+            Assert.False(bindingContext.ModelState.IsValid);
+            Assert.Equal("Input string was not in a correct format.", bindingContext.ModelState["theModelName"].Errors[0].ErrorMessage);
         }
 
         // TODO: TypeConverter