diff --git a/backend/workflow_executor.py b/backend/workflow_executor.py
index e5a7152..693c7ed 100644
--- a/backend/workflow_executor.py
+++ b/backend/workflow_executor.py
@@ -398,8 +398,16 @@ def execute_logic_node(
     started_at = datetime.utcnow().isoformat()
 
     try:
-        if not node.condition:
-            raise ValueError(f"Logic node {node.id} has no condition")
+        if not node.condition or not node.condition.expression:
+            error_msg = f"Logic node {node.id} has no condition/expression defined"
+            logger.error(error_msg)
+            return NodeExecutionState(
+                node_id=node.id,
+                status=NodeStatus.FAILED,
+                error=error_msg,
+                started_at=started_at,
+                completed_at=datetime.utcnow().isoformat()
+            )
 
         # 1. Evaluiere Bedingung
         result, error = evaluate_logic_expression(node.condition.expression, context)