--- ../src_base/common/net/minecraft/src/WorldGenBigMushroom.java
+++ ../src_work/common/net/minecraft/src/WorldGenBigMushroom.java
@@ -54,7 +54,9 @@
                         {
                             var13 = par1World.getBlockId(var11, var9, var12);
 
-                            if (var13 != 0 && var13 != Block.leaves.blockID)
+                            Block block = Block.blocksList[var13];
+                            
+                            if (var13 != 0 && block != null && !block.isLeaves(par1World, var11, var9, var12))
                             {
                                 var8 = false;
                             }
@@ -181,7 +183,9 @@
                                     var15 = 0;
                                 }
 
-                                if ((var15 != 0 || par4 >= par4 + var7 - 1) && !Block.opaqueCubeLookup[par1World.getBlockId(var13, var11, var14)])
+                                Block block = Block.blocksList[par1World.getBlockId(var13, var11, var14)];
+
+                                if ((var15 != 0 || par4 >= par4 + var7 - 1) && (block == null || block.canBeReplacedByLeaves(par1World, var13, var11, var14)))
                                 {
                                     this.setBlockAndMetadata(par1World, var13, var11, var14, Block.mushroomCapBrown.blockID + var6, var15);
                                 }
@@ -193,7 +197,9 @@
                     {
                         var12 = par1World.getBlockId(par3, par4 + var11, par5);
 
-                        if (!Block.opaqueCubeLookup[var12])
+                        Block block = Block.blocksList[var12];
+
+                        if (block == null || block.canBeReplacedByLeaves(par1World, par3, par4 + var11, par5))
                         {
                             this.setBlockAndMetadata(par1World, par3, par4 + var11, par5, Block.mushroomCapBrown.blockID + var6, 10);
                         }