diff --git a/src/runtime/methodbinder.cs b/src/runtime/methodbinder.cs
index 2cf548f48..17cfbaadd 100644
--- a/src/runtime/methodbinder.cs
+++ b/src/runtime/methodbinder.cs
@@ -586,7 +586,7 @@ static Type TryComputeClrArgumentType(Type parameterType, IntPtr argument, bool
             if (clrtype != null)
             {
                 var typematch = false;
-                if ((parameterType != typeof(object)) && (parameterType != clrtype))
+                if (parameterType != typeof(object) && parameterType != clrtype && Nullable.GetUnderlyingType(parameterType) != clrtype)
                 {
                     IntPtr pytype = Converter.GetPythonTypeByAlias(parameterType);
                     pyoptype = Runtime.PyObject_Type(argument);