diff --git a/testtools/testcase.py b/testtools/testcase.py
index 2ec2296a..b30c0701 100644
--- a/testtools/testcase.py
+++ b/testtools/testcase.py
@@ -172,7 +172,7 @@ def gather_details(source_dict, target_dict):
 class UseFixtureProtocol(Protocol):
     def setUp(self) -> Any: ...
     def cleanUp(self) -> Any: ...
-    def getDetails(self) -> dict[str, content.Content]: ...
+    def getDetails(self) -> dict: ...
 
 
 UseFixtureT = TypeVar("UseFixtureT", bound=UseFixtureProtocol)