diff --git a/tcp_syni.nim b/tcp_syni.nim
index 619143b..df5536e 100644
--- a/tcp_syni.nim
+++ b/tcp_syni.nim
@@ -174,10 +174,10 @@ proc predictPortRange(dstPorts: seq[Port]): seq[Port] =
     result[i] = Port(basePort + i.uint16)
 
 proc cleanup*(puncher: TcpSyniPuncher) {.async.} =
-  for attempt in puncher.connectAttempts:
-    await attempt.deleteFirewallRules()
-  for attempt in puncher.acceptAttempts:
-    await attempt.deleteFirewallRules()
+  while puncher.connectAttempts.len() != 0:
+    await puncher.connectAttempts.pop().deleteFirewallRules()
+  while puncher.acceptAttempts.len() != 0:
+    await puncher.connectAttempts.pop().deleteFirewallRules()
 
 proc doConnect(srcIp: IpAddress, srcPort: Port, dstIp: IpAddress, dstPort: Port,
                future: Future[AsyncSocket]) {.async.} =