diff --git a/.ci/compute_projects.py b/.ci/compute_projects.py
index 8bae8359ff23..e9c43a4df8ec 100644
--- a/.ci/compute_projects.py
+++ b/.ci/compute_projects.py
@@ -112,6 +112,8 @@ PROJECT_CHECK_TARGETS = {
     "polly": "check-polly",
 }
 
+RUNTIMES = {"libcxx", "libcxxabi", "libunwind"}
+
 
 def _add_dependencies(projects: Set[str]) -> Set[str]:
     projects_with_dependents = set(projects)
@@ -131,6 +133,8 @@ def _compute_projects_to_test(modified_projects: Set[str], platform: str) -> Set
         # Skip all projects where we cannot run tests.
         if modified_project not in PROJECT_CHECK_TARGETS:
             continue
+        if modified_project in RUNTIMES:
+            continue
         projects_to_test.add(modified_project)
         if modified_project not in DEPENDENTS_TO_TEST:
             continue
diff --git a/.ci/compute_projects_test.py b/.ci/compute_projects_test.py
index 4e79f9368539..4afc121f18c4 100644
--- a/.ci/compute_projects_test.py
+++ b/.ci/compute_projects_test.py
@@ -161,6 +161,15 @@ class TestComputeProjects(unittest.TestCase):
         self.assertEqual(env_variables["runtimes_to_build"], "")
         self.assertEqual(env_variables["runtimes_check_targets"], "")
 
+    def test_blah(self):
+        env_variables = compute_projects.get_env_variables(
+            [".ci/compute_projects.py", "libcxx/CMakeLists.txt"], "Linux"
+        )
+        self.assertEqual(env_variables["projects_to_build"], "")
+        self.assertEqual(env_variables["project_check_targets"], "")
+        self.assertEqual(env_variables["runtimes_to_build"], "")
+        self.assertEqual(env_variables["runtimes_check_targets"], "")
+
 
 if __name__ == "__main__":
     unittest.main()