diff --git a/pkgs/development/python-modules/cytoolz/default.nix b/pkgs/development/python-modules/cytoolz/default.nix
index 0e72ecaa825..4e862d26092 100644
--- a/pkgs/development/python-modules/cytoolz/default.nix
+++ b/pkgs/development/python-modules/cytoolz/default.nix
@@ -22,9 +22,8 @@ buildPythonPackage rec {
   checkInputs = [ nose ];
   propagatedBuildInputs = [ toolz ];
 
-  # Failing test https://github.com/pytoolz/cytoolz/issues/122
   checkPhase = ''
-    NOSE_EXCLUDE=test_introspect_builtin_modules nosetests -v $out/${python.sitePackages}
+    nosetests -v $out/${python.sitePackages}
   '';
 
   meta = {