diff --git a/pyadjoint/overloaded_type.py b/pyadjoint/overloaded_type.py
index a6a02f68..0f96667e 100644
--- a/pyadjoint/overloaded_type.py
+++ b/pyadjoint/overloaded_type.py
@@ -308,6 +308,7 @@ def _ad_dim(self):
         """
         raise NotImplementedError
 
+    @property
     def _ad_str(self):
         """Return the string representation of the block variable.