diff --git a/tests/functional/common/init.sh b/tests/functional/common/init.sh
index 19cef5af9..405ba3090 100755
--- a/tests/functional/common/init.sh
+++ b/tests/functional/common/init.sh
@@ -9,7 +9,7 @@ if isTestOnNixOS; then
 
   export NIX_USER_CONF_FILES="$test_nix_conf_dir/nix.conf"
   mkdir -p "$test_nix_conf_dir" "$TEST_HOME"
-  ! test -e "$test_nix_conf"
+  (! test -e "$test_nix_conf")
   cat > "$test_nix_conf_dir/nix.conf" <<EOF
 experimental-features = nix-command flakes
 flake-registry = $TEST_ROOT/registry.json