diff --git a/Airlock/Airlock.cs b/Airlock/Airlock.cs
index 9db601d..0cb214e 100644
--- a/Airlock/Airlock.cs
+++ b/Airlock/Airlock.cs
@@ -140,6 +140,7 @@ namespace IngameScript
 
             public IEnumerator<bool> CycleAirlock()
             {
+                if (Cycling) yield break;
                 Cycling = true;
                 setLights(AirlockLightState.Cycling);