--- ../src_base/common/net/minecraft/src/WorldGenTaiga2.java
+++ ../src_work/common/net/minecraft/src/WorldGenTaiga2.java
@@ -45,7 +45,9 @@
                         {
                             var15 = par1World.getBlockId(var13, var11, var14);
 
-                            if (var15 != 0 && var15 != Block.leaves.blockID)
+                            Block block = Block.blocksList[var15];
+
+                            if (var15 != 0 && block != null && !block.isLeaves(par1World, var13, var11, var14))
                             {
                                 var10 = false;
                             }
@@ -87,7 +89,10 @@
                             {
                                 int var20 = var19 - par5;
 
-                                if ((Math.abs(var18) != var21 || Math.abs(var20) != var21 || var21 <= 0) && !Block.opaqueCubeLookup[par1World.getBlockId(var17, var16, var19)])
+                                Block block = Block.blocksList[par1World.getBlockId(var17, var16, var19)];
+
+                                if ((Math.abs(var18) != var21 || Math.abs(var20) != var21 || var21 <= 0) && 
+                                    (block == null || block.canBeReplacedByLeaves(par1World, var17, var16, var19)))
                                 {
                                     this.setBlockAndMetadata(par1World, var17, var16, var19, Block.leaves.blockID, 1);
                                 }
@@ -117,7 +122,9 @@
                     {
                         var17 = par1World.getBlockId(par3, par4 + var16, par5);
 
-                        if (var17 == 0 || var17 == Block.leaves.blockID)
+                        Block block = Block.blocksList[var17];
+
+                        if (var17 == 0 || block == null || block.isLeaves(par1World, par3, par4 + var16, par5))
                         {
                             this.setBlockAndMetadata(par1World, par3, par4 + var16, par5, Block.wood.blockID, 1);
                         }