diff --git a/nix/default.nix b/nix/default.nix
index 891f96a366e7aceec214833d75f646a4b71ff08a..e96878f95a6dc08c5936933d878c64264e08039a 100644
--- a/nix/default.nix
+++ b/nix/default.nix
@@ -19,6 +19,7 @@ plugins.helpers.simple_plugin
      configure_options = "-with-clang-includedir=${unstablePckgs.llvmPackages_9.clang-unwrapped}";
      preFramaCTests = ''
        echo Configuring Why3 for frama-clang.
+       export HOME=$(mktemp -d)
        why3 config --full-config
      '';
    }