diff --git a/lib/spack/spack/test/concretize_preferences.py b/lib/spack/spack/test/concretize_preferences.py
index 4d9b2a4a767..5c80a20b9f2 100644
--- a/lib/spack/spack/test/concretize_preferences.py
+++ b/lib/spack/spack/test/concretize_preferences.py
@@ -200,11 +200,13 @@ def test_config_set_pkg_property_new(self, mutable_mock_repo):
         update_packages(
             "mpileaks",
             "package_attributes",
-            {"x": "1", "y": "true"},
+            {"x": "1", "y": "true", "w": "yes", "z": "yesterday"},
         )
         spec = concretize("mpileaks")
         assert spec.package.x == 1
         assert spec.package.y == True
+        assert spec.package.w == True
+        assert spec.package.z == "yesterday"
 
     def test_config_set_pkg_property_collecton_unsupported(self, mutable_mock_repo):
         """Test that an error is raised if you attempt to assign a list value"""