diff --git a/polymorphic/__init__.py b/polymorphic/__init__.py
index a1219bf..07ee3fa 100644
--- a/polymorphic/__init__.py
+++ b/polymorphic/__init__.py
@@ -9,5 +9,8 @@ Please see LICENSE and AUTHORS for more information.
 
 import pkg_resources
 
+try:
+    __version__ = pkg_resources.require("django-polymorphic")[0].version
+except pkg_resources.DistributionNotFound:
+    __version__ = None  # for RTD among others
 
-__version__ = pkg_resources.require("django-polymorphic")[0].version