diff --git a/src/GameLogic/PlugIns/PeriodicTasks/MiniGameStartBasePlugIn.cs b/src/GameLogic/PlugIns/PeriodicTasks/MiniGameStartBasePlugIn.cs
index 7c3e6dc..e8e77fe 100644
--- a/src/GameLogic/PlugIns/PeriodicTasks/MiniGameStartBasePlugIn.cs
+++ b/src/GameLogic/PlugIns/PeriodicTasks/MiniGameStartBasePlugIn.cs
@@ -102,6 +102,14 @@ public abstract class MiniGameStartBasePlugIn<TConfiguration, TGameState> : Peri
                 return;
             }
 
+            // Sub-minute entrance windows (e.g. a 30s test window) have (int)TotalMinutes == 0, so the
+            // per-minute loop below would send nothing and players would get no "event opened" notification.
+            // Announce once up front in that case (>= 1 minute windows are unaffected).
+            if ((int)enterDuration.TotalMinutes == 0 && this.Configuration?.EntranceOpenedMessage is { } shortOpenMessage)
+            {
+                await state.Context.SendGlobalNotificationAsync(string.Format(shortOpenMessage, 1)).ConfigureAwait(false);
+            }
+
             for (var remainingMinutes = (int)enterDuration.TotalMinutes; remainingMinutes > 0; remainingMinutes--)
             {
                 if (this.Configuration?.EntranceOpenedMessage is { } openMessage)