diff --git a/dagflow/dagflow.py b/dagflow/dagflow.py
index e14e5fa..287cfbd 100644
--- a/dagflow/dagflow.py
+++ b/dagflow/dagflow.py
@@ -292,7 +292,7 @@ where backid=${backid}$
 	async def auto_assign(self, sor, inst, ne, node):
 		recs = await env.get_org_users(sor, inst.org_id, ne.role)
 		if recs:
-			i = randint(len(recs) - 1)
+			i = randint(0, len(recs) - 1)
 			await sor.U('node_execution', {
 				'id':ne.id,
 				'assignee': recs[i].id
@@ -501,7 +501,7 @@ where instance_id=${instance_id}$
 def get_engine():
 	env = ServerEnv()
 	cnt = len(env.flow_engines)
-	id = randint(cnt-1)
+	id = randint(0, cnt-1)
 	return env.flow_engines[id]
 
 async def add_new_workflow(request, params_kw={}):