diff --git a/dataproperty/__init__.py b/dataproperty/__init__.py
index 424e238..91e6321 100644
--- a/dataproperty/__init__.py
+++ b/dataproperty/__init__.py
@@ -44,6 +44,7 @@
 from ._type import (
     NoneType,
     StringType,
+    NullStringType,
     IntegerType,
     FloatType,
     DateTimeType,