diff --git a/nix/default.nix b/nix/default.nix
index 588b4df87e0e9a7474cfe6f0acb43687fa38274f..c9fc3d597ad518ae38ba344b92365c94bdf13fa3 100644
--- a/nix/default.nix
+++ b/nix/default.nix
@@ -170,6 +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
                bin/ptests.opt -error-code -config qualif src/plugins/wp/tests
         '';
         installPhase = ''