diff --git a/pgactivity/types.py b/pgactivity/types.py
index 8f6852de..6620379a 100644
--- a/pgactivity/types.py
+++ b/pgactivity/types.py
@@ -885,6 +885,8 @@ class LockType(enum.Enum):
 
     def __str__(self) -> str:
         # Custom str(self) for transparent rendering in views.
+        assert isinstance(self.name, str)
+        # TODO ^ remove this assert for mypy > 0.991
         return self.name