diff --git a/properdocs/tests/cli_tests.py b/properdocs/tests/cli_tests.py
index cf7ea444..d6345d11 100644
--- a/properdocs/tests/cli_tests.py
+++ b/properdocs/tests/cli_tests.py
@@ -1,5 +1,6 @@
 #!/usr/bin/env python
 
+import gc
 import io
 import logging
 import unittest
@@ -14,6 +15,12 @@ class CLITests(unittest.TestCase):
     def setUp(self):
         self.runner = CliRunner()
 
+    def tearDown(self):
+        super().tearDown()
+        # Cleanup of CliRunner, if done non-deterministically, can mess up tests that follow after.
+        del self.runner
+        gc.collect()
+
     @mock.patch('properdocs.commands.serve.serve', autospec=True)
     def test_serve_default(self, mock_serve):
         result = self.runner.invoke(cli.cli, ["serve"], catch_exceptions=False)