diff --git a/src/runtime/converter.cs b/src/runtime/converter.cs
index aa4ed6a80..62e091d31 100644
--- a/src/runtime/converter.cs
+++ b/src/runtime/converter.cs
@@ -698,19 +698,10 @@ private static bool ToPrimitive(IntPtr value, Type obType, out object result, bo
 
                 case TypeCode.UInt64:
                     {
-                        op = value;
-                        if (Runtime.PyObject_TYPE(value) != Runtime.PyLongType)
-                        {
-                            op = Runtime.PyNumber_Long(value);
-                            if (op == IntPtr.Zero)
-                            {
-                                goto convert_error;
-                            }
-                        }
-                        ulong num = Runtime.PyLong_AsUnsignedLongLong(op);
+                        ulong num = Runtime.PyLong_AsUnsignedLongLong(value);
                         if (num == ulong.MaxValue && Exceptions.ErrorOccurred())
                         {
-                            goto overflow;
+                            goto convert_error;
                         }
                         result = num;
                         return true;
diff --git a/src/tests/test_conversion.py b/src/tests/test_conversion.py
index 6b152025d..3b290b947 100644
--- a/src/tests/test_conversion.py
+++ b/src/tests/test_conversion.py
@@ -382,7 +382,10 @@ def test_uint64_conversion():
     ob.UInt64Field = System.UInt64(0)
     assert ob.UInt64Field == 0
 
-    with pytest.raises(ValueError):
+    with pytest.raises(TypeError):
+        ConversionTest().UInt64Field = 0.5
+
+    with pytest.raises(TypeError):
         ConversionTest().UInt64Field = "spam"
 
     with pytest.raises(TypeError):