diff --git a/nix/default.nix b/nix/default.nix
index c9fc3d597ad518ae38ba344b92365c94bdf13fa3..5b892f99684c6fbc9350df9a936c175b73a09bdd 100644
--- a/nix/default.nix
+++ b/nix/default.nix
@@ -170,9 +170,9 @@ rec {
                mkdir home
                HOME=$(pwd)/home
                why3 config --full-config
-               FRAMAC_WP_CACHE=replay
-               FRAMAC_WP_CACHEDIR=${plugins.wp-cache.src};
                make src/plugins/wp/tests/test_config_qualif
+               export FRAMAC_WP_CACHE=replay
+               export FRAMAC_WP_CACHEDIR=${plugins.wp-cache.src}
                bin/ptests.opt -error-code -config qualif src/plugins/wp/tests
         '';
         installPhase = ''