--- /home/matt/mc-dev-private//net/minecraft/server/TileEntityPiston.java	2015-02-26 22:40:23.163608133 +0000
+++ src/main/java/net/minecraft/server/TileEntityPiston.java	2015-02-26 22:40:23.163608133 +0000
@@ -104,6 +104,7 @@
     }
 
     public void c() {
+        if (this.world == null) return; // CraftBukkit
         this.j = this.i;
         if (this.j >= 1.0F) {
             this.a(1.0F, 0.25F);