diff --git a/tests/supplementary-groups.sh b/tests/supplementary-groups.sh
index 474ba7503..d18fb2414 100644
--- a/tests/supplementary-groups.sh
+++ b/tests/supplementary-groups.sh
@@ -5,13 +5,13 @@ requireSandboxSupport
 if ! command -p -v unshare; then skipTest "Need unshare"; fi
 needLocalStore "The test uses --store always so we would just be bypassing the daemon"
 
-# Avoid store dir being inside sandbox build-dir
-unset NIX_STORE_DIR
-unset NIX_STATE_DIR
-
 unshare --mount --map-root-user bash <<EOF
   source common.sh
 
+  # Avoid store dir being inside sandbox build-dir
+  unset NIX_STORE_DIR
+  unset NIX_STATE_DIR
+
   setLocalStore () {
     export NIX_REMOTE=\$TEST_ROOT/\$1
     mkdir -p \$NIX_REMOTE