diff --git a/src/python/pants/core/util_rules/external_tool_test.py b/src/python/pants/core/util_rules/external_tool_test.py
index 8e64a4b97f8..7942024409d 100644
--- a/src/python/pants/core/util_rules/external_tool_test.py
+++ b/src/python/pants/core/util_rules/external_tool_test.py
@@ -146,7 +146,7 @@ def rule_runner():
     )
 
 
-def test_export(rule_runner):
+def test_export(rule_runner) -> None:
     """Tests export_external_tool.
 
     Ensures we locate the class and prepare the Digest correctly