diff --git a/dagflow/dagflow.py b/dagflow/dagflow.py
index 8dd1aba..2c06260 100644
--- a/dagflow/dagflow.py
+++ b/dagflow/dagflow.py
@@ -356,9 +356,9 @@ where backid=${backid}$
 			if m_on:
 				on_array = safe_eval_condition(m_on, ctx)
 				for e in on_array:
-					nnodes.add((edge['to'], str(e)))
+					nnodes.append((edge['to'], str(e)))
 			else:
-				nnodes.add(edge['to'], None)
+				nnodes.append(edge['to'], None)
 
 		for node_id, ctx_ext in nnodes:
 			node = dsl['nodes'][node_id]