diff --git a/pkgs/development/python-modules/pycrypto/default.nix b/pkgs/development/python-modules/pycrypto/default.nix
index 72000acad17e..c79abd49ec1d 100644
--- a/pkgs/development/python-modules/pycrypto/default.nix
+++ b/pkgs/development/python-modules/pycrypto/default.nix
@@ -9,7 +9,7 @@ buildPythonPackage rec {
   format = "setuptools";
 
   # Cannot build wheel otherwise (zip 1980 issue)
-  SOURCE_DATE_EPOCH = 315532800;
+  env.SOURCE_DATE_EPOCH = 315532800;
 
   # We need to have a dist-info folder, so let's create one with setuptools
   unpackPhase = ''