diff --git a/common/net/minecraftforge/common/ForgeChunkManager.java b/common/net/minecraftforge/common/ForgeChunkManager.java
index d12b50520..ac5026271 100644
--- a/common/net/minecraftforge/common/ForgeChunkManager.java
+++ b/common/net/minecraftforge/common/ForgeChunkManager.java
@@ -403,7 +403,7 @@ public class ForgeChunkManager
         }
         if (ticket.requestedChunks!=null)
         {
-            for (ChunkCoordIntPair chunk : ticket.requestedChunks)
+            for (ChunkCoordIntPair chunk : ImmutableSet.copyOf(ticket.requestedChunks))
             {
                 unforceChunk(ticket, chunk);
             }