diff --git a/Content.Server/Procedural/DungeonJob/DungeonJob.PostGenBiome.cs b/Content.Server/Procedural/DungeonJob/DungeonJob.PostGenBiome.cs
index 8a40191e02..63905cfd66 100644
--- a/Content.Server/Procedural/DungeonJob/DungeonJob.PostGenBiome.cs
+++ b/Content.Server/Procedural/DungeonJob/DungeonJob.PostGenBiome.cs
@@ -34,7 +34,7 @@ public sealed partial class DungeonJob
 
             if (dunGen.TileMask is not null)
             {
-                if (dunGen.TileMask.Contains(((ContentTileDefinition) _tileDefManager[tileRef.Value.Tile.TypeId]).ID))
+                if (!dunGen.TileMask.Contains(((ContentTileDefinition) _tileDefManager[tileRef.Value.Tile.TypeId]).ID))
                     continue;
             }