--- ../src-base/minecraft/net/minecraft/world/storage/WorldInfo.java
+++ ../src-work/minecraft/net/minecraft/world/storage/WorldInfo.java
@@ -52,6 +52,7 @@
     private int field_176155_J;
     private GameRules field_82577_x;
     private static final String __OBFID = "CL_00000587";
+    private java.util.Map<String, net.minecraft.nbt.NBTBase> additionalProperties;
 
     protected WorldInfo()
     {
@@ -803,4 +804,24 @@
             }
         });
     }
+
+    /**
+     * Allow access to additional mod specific world based properties
+     * Used by FML to store mod list associated with a world, and maybe an id map
+     * Used by Forge to store the dimensions available to a world
+     * @param additionalProperties
+     */
+    public void setAdditionalProperties(java.util.Map<String,net.minecraft.nbt.NBTBase> additionalProperties)
+    {
+        // one time set for this
+        if (this.additionalProperties == null)
+        {
+            this.additionalProperties = additionalProperties;
+        }
+    }
+
+    public net.minecraft.nbt.NBTBase getAdditionalProperty(String additionalProperty)
+    {
+        return this.additionalProperties!=null? this.additionalProperties.get(additionalProperty) : null;
+    }
 }
