diff --git a/src/Microsoft.AspNet.Razor/TagHelpers/TypeBasedTagHelperDescriptorComparer.cs b/src/Microsoft.AspNet.Razor/TagHelpers/TypeBasedTagHelperDescriptorComparer.cs
index 2e3356ab17..bd0efdc0fa 100644
--- a/src/Microsoft.AspNet.Razor/TagHelpers/TypeBasedTagHelperDescriptorComparer.cs
+++ b/src/Microsoft.AspNet.Razor/TagHelpers/TypeBasedTagHelperDescriptorComparer.cs
@@ -42,7 +42,8 @@ namespace Microsoft.AspNet.Razor.TagHelpers
                 return true;
             }
 
-            return string.Equals(descriptorX.AssemblyName, descriptorY.AssemblyName, StringComparison.Ordinal) &&
+            return descriptorX != null &&
+                string.Equals(descriptorX.AssemblyName, descriptorY.AssemblyName, StringComparison.Ordinal) &&
                 string.Equals(descriptorX.TypeName, descriptorY.TypeName, StringComparison.Ordinal);
         }
 
diff --git a/test/Microsoft.AspNet.Razor.Runtime.Test/TagHelpers/CaseSensitiveTagHelperAttributeComparer.cs b/test/Microsoft.AspNet.Razor.Runtime.Test/TagHelpers/CaseSensitiveTagHelperAttributeComparer.cs
index 7625c9fe89..a5ba8e300d 100644
--- a/test/Microsoft.AspNet.Razor.Runtime.Test/TagHelpers/CaseSensitiveTagHelperAttributeComparer.cs
+++ b/test/Microsoft.AspNet.Razor.Runtime.Test/TagHelpers/CaseSensitiveTagHelperAttributeComparer.cs
@@ -18,9 +18,13 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
 
         public bool Equals(IReadOnlyTagHelperAttribute attributeX, IReadOnlyTagHelperAttribute attributeY)
         {
-            return
-                attributeX == attributeY ||
-                // Normal comparer doesn't care about the Name case, in tests we do.
+            if (attributeX == attributeY)
+            {
+                return true;
+            }
+
+            // Normal comparer (TagHelperAttribute.Equals()) doesn't care about the Name case, in tests we do.
+            return attributeX != null &&
                 string.Equals(attributeX.Name, attributeY.Name, StringComparison.Ordinal) &&
                 Equals(attributeX.Value, attributeY.Value);
         }