Don't wrap the y coordinate in World.getBlockAt

src/main/java/org/bukkit/craftbukkit/CraftWorld.java

@@ -82,7 +82,7 @@ public class CraftWorld implements World {
     }
 
     public Block getBlockAt(int x, int y, int z) {
-        return getChunkAt(x >> 4, z >> 4).getBlock(x & 0xF, y & 0xFF, z & 0xF);
+        return getChunkAt(x >> 4, z >> 4).getBlock(x & 0xF, y, z & 0xF);
     }
 
     public int getBlockTypeIdAt(int x, int y, int z) {