diff --git a/src/idom/core/layout.py b/src/idom/core/layout.py
index db861142d..5f7d667ad 100644
--- a/src/idom/core/layout.py
+++ b/src/idom/core/layout.py
@@ -136,7 +136,7 @@ async def render(self) -> LayoutUpdate:
             except KeyError:
                 logger.debug(
                     "Did not render component with model state ID "
-                    "{model_state_id!r} - component already unmounted"
+                    f"{model_state_id!r} - component already unmounted"
                 )
             else:
                 return self._create_layout_update(model_state)