diff --git a/lib/spack/spack/test/concretize.py b/lib/spack/spack/test/concretize.py
index 3c36c06a232..50dbaa8eb8d 100644
--- a/lib/spack/spack/test/concretize.py
+++ b/lib/spack/spack/test/concretize.py
@@ -2824,10 +2824,12 @@ def test_git_ref_version_can_be_reused(
     )
     # override gcc-runtime dep and make all installs reusable
     monkeypatch.setattr(spack.solver.asp, "_has_runtime_dependencies", mock_runtime_dependencies)
+
     first_spec = spack.spec.Spec(
         "git-test-commit@git.v1.0=1.0+generic_install+feature"
     ).concretized()
     first_spec.package.do_install(fake=True, explicit=True)
+
     with spack.config.override("concretizer:reuse", True):
         second_spec = spack.spec.Spec(
             "git-test-commit@git.v1.0=1.0+generic_install~feature"
@@ -2836,12 +2838,14 @@ def test_git_ref_version_can_be_reused(
         assert second_spec.dag_hash() != first_spec.dag_hash()
 
 
+@pytest.mark.only_clingo("clingo only re-use feature being tested")
 def test_reuse_prefers_standard_over_git_versions(
     monkeypatch, mock_packages, install_mockery_mutable_config, mock_git_version_info
 ):
     """
     order matters in this test. typically re-use would pick the last installed match
     but we want to prefer the standard version over git ref based versions
+    so install git ref last and ensure it is not picked up by re-use
     """
     repo_path, filename, commits = mock_git_version_info
     monkeypatch.setattr(
@@ -2849,12 +2853,15 @@ def test_reuse_prefers_standard_over_git_versions(
     )
     # override gcc-runtime dep and make all installs reusable
     monkeypatch.setattr(spack.solver.asp, "_has_runtime_dependencies", mock_runtime_dependencies)
+
     standard_spec = spack.spec.Spec("git-test-commit@1.0+generic_install+feature").concretized()
     standard_spec.package.do_install(fake=True, explicit=True)
+
     git_spec = spack.spec.Spec(
         "git-test-commit@git.v1.0=1.0+generic_install+feature"
     ).concretized()
     git_spec.package.do_install(fake=True, explicit=True)
+
     with spack.config.override("concretizer:reuse", True):
         test_spec = spack.spec.Spec("git-test-commit@1.0+generic_install").concretized()
         assert git_spec.dag_hash() != test_spec.dag_hash()