--- ../src-base/minecraft/net/minecraft/world/storage/WorldInfo.java
+++ ../src-work/minecraft/net/minecraft/world/storage/WorldInfo.java
@@ -63,8 +63,9 @@
     private double field_176153_H = 0.2D;
     private int field_176154_I = 5;
     private int field_176155_J = 15;
     private GameRules field_82577_x = new GameRules();
+    private java.util.Map<String, net.minecraft.nbt.NBTBase> additionalProperties;
 
     protected WorldInfo()
     {
@@ -366,6 +367,7 @@
         p_76064_1_.func_74780_a("BorderSizeLerpTarget", this.field_176148_F);
         p_76064_1_.func_74780_a("BorderWarningBlocks", (double)this.field_176154_I);
         p_76064_1_.func_74780_a("BorderWarningTime", (double)this.field_176155_J);
+        net.minecraftforge.fml.common.FMLCommonHandler.instance().getDataFixer().writeVersionData(p_76064_1_);
 
         if (this.field_176158_z != null)
         {
@@ -708,6 +711,7 @@
 
     public void func_176144_a(EnumDifficulty p_176144_1_)
     {
+        net.minecraftforge.common.ForgeHooks.onDifficultyChange(p_176144_1_, this.field_176158_z);
         this.field_176158_z = p_176144_1_;
     }
 
@@ -805,18 +809,49 @@
             }
         });
     }
+    /**
+     * 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;
+    }
+