diff --git a/pkgs/development/python-modules/btrees/default.nix b/pkgs/development/python-modules/btrees/default.nix
index 44e96b5ff30..8e69a207628 100644
--- a/pkgs/development/python-modules/btrees/default.nix
+++ b/pkgs/development/python-modules/btrees/default.nix
@@ -1,4 +1,4 @@
-{ stdenv, buildPythonPackage, persistent, zope_interface, transaction }:
+{ stdenv, fetchPypi, buildPythonPackage, persistent, zope_interface, transaction }:
 
 buildPythonPackage rec {
   pname = "BTrees";