diff --git a/src/graph_scheduler/condition.py b/src/graph_scheduler/condition.py
index 0858938..e37d9a8 100644
--- a/src/graph_scheduler/condition.py
+++ b/src/graph_scheduler/condition.py
@@ -3227,7 +3227,7 @@ def _nodes_already_valid(self, graph):
     def _validate_graph(self, graph):
         super()._validate_graph(graph)
 
-        already_valid = self._nodes_already_valid(graph)
+        already_valid = [repr(n) for n in self._nodes_already_valid(graph)]
         try:
             already_valid = sorted(already_valid)
         except TypeError: