Recompiling IC & java.lang.NoClassDefFoundError

    I had succefully decompiled IC2, and changed only one raw in only one class.
    Before reobf everything works.


    Recompile - > reobf
    And puted this (only one) class in original IC2.
    After that:

    Code
    cpw.mods.fml.common.LoaderException: java.lang.NoClassDefFoundError: ic2/core/item/tool/ItemToolWrench	at cpw.mods.fml.common.LoadController.transition(LoadController.java:130)	at cpw.mods.fml.common.Loader.loadMods(Loader.java:506)	at cpw.mods.fml.server.FMLServerHandler.beginServerLoading(FMLServerHandler.java:86)	at cpw.mods.fml.common.FMLCommonHandler.onServerStart(FMLCommonHandler.java:351)	at ho.c(DedicatedServer.java:86)	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:724)	at fy.run(ThreadMinecraftServer.java:16)Caused by: java.lang.NoClassDefFoundError: ic2/core/item/tool/ItemToolWrench	at ic2.core.IC2.load(IC2.java:621)	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)	at java.lang.reflect.Method.invoke(Unknown Source)	at cpw.mods.fml.common.FMLModContainer.handleModStateEvent(FMLModContainer.java:487)	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)	at java.lang.reflect.Method.invoke(Unknown Source)	at com.google.common.eventbus.EventHandler.handleEvent(EventHandler.java:69)	at com.google.common.eventbus.SynchronizedEventHandler.handleEvent(SynchronizedEventHandler.java:45)	at com.google.common.eventbus.EventBus.dispatch(EventBus.java:317)	at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:300)	at com.google.common.eventbus.EventBus.post(EventBus.java:268)	at cpw.mods.fml.common.LoadController.propogateStateMessage(LoadController.java:153)	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)	at java.lang.reflect.Method.invoke(Unknown Source)	at com.google.common.eventbus.EventHandler.handleEvent(EventHandler.java:69)	at com.google.common.eventbus.SynchronizedEventHandler.handleEvent(SynchronizedEventHandler.java:45)	at com.google.common.eventbus.EventBus.dispatch(EventBus.java:317)	at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:300)	at com.google.common.eventbus.EventBus.post(EventBus.java:268)	at cpw.mods.fml.common.LoadController.distributeStateMessage(LoadController.java:86)	at cpw.mods.fml.common.Loader.loadMods(Loader.java:505)	... 5 more


    Why does it so? What can be wrong?
    I checked, ic had this class, i don't modifed package.