diff --git a/pkgs/development/python-modules/pygit2/default.nix b/pkgs/development/python-modules/pygit2/default.nix
index 76673d096c22..0d793e367bf8 100644
--- a/pkgs/development/python-modules/pygit2/default.nix
+++ b/pkgs/development/python-modules/pygit2/default.nix
@@ -50,7 +50,7 @@ buildPythonPackage rec {
 
   # Tests require certificates
   # https://github.com/NixOS/nixpkgs/pull/72544#issuecomment-582674047
-  SSL_CERT_FILE = "${cacert}/etc/ssl/certs/ca-bundle.crt";
+  env.SSL_CERT_FILE = "${cacert}/etc/ssl/certs/ca-bundle.crt";
 
   pythonImportsCheck = [ "pygit2" ];