diff --git a/lib/spack/spack/test/concretize.py b/lib/spack/spack/test/concretize.py
index eba86d14fc..2818aad042 100644
--- a/lib/spack/spack/test/concretize.py
+++ b/lib/spack/spack/test/concretize.py
@@ -203,7 +203,9 @@ def change(self, changes=None):
                 # TODO: in case tests using this fixture start failing.
                 if sys.modules.get("spack.pkg.changing.changing"):
                     del sys.modules["spack.pkg.changing.changing"]
+                if sys.modules.get("spack.pkg.changing.root"):
                     del sys.modules["spack.pkg.changing.root"]
+                if sys.modules.get("spack.pkg.changing"):
                     del sys.modules["spack.pkg.changing"]
 
                 # Change the recipe
@@ -1604,7 +1606,9 @@ def test_installed_version_is_selected_only_for_reuse(
         assert not new_root["changing"].satisfies("@1.0")
 
     @pytest.mark.regression("28259")
-    def test_reuse_with_unknown_namespace_dont_raise(self, mock_custom_repository):
+    def test_reuse_with_unknown_namespace_dont_raise(
+        self, temporary_store, mock_custom_repository
+    ):
         with spack.repo.use_repositories(mock_custom_repository, override=False):
             s = Spec("c").concretized()
             assert s.namespace != "builtin.mock"
@@ -1615,8 +1619,8 @@ def test_reuse_with_unknown_namespace_dont_raise(self, mock_custom_repository):
         assert s.namespace == "builtin.mock"
 
     @pytest.mark.regression("28259")
-    def test_reuse_with_unknown_package_dont_raise(self, tmpdir, monkeypatch):
-        builder = spack.repo.MockRepositoryBuilder(tmpdir, namespace="myrepo")
+    def test_reuse_with_unknown_package_dont_raise(self, tmpdir, temporary_store, monkeypatch):
+        builder = spack.repo.MockRepositoryBuilder(tmpdir.mkdir("mock.repo"), namespace="myrepo")
         builder.add_package("c")
         with spack.repo.use_repositories(builder.root, override=False):
             s = Spec("c").concretized()