No, this is also trigger error Unknow option. ".\jre64\bin\java.exe" -Xms1024m -Xmx1024m -Djava.library.path=./ -cp lwjgl.jar;lwjgl_util.jar;./ zombie.gameStates.MainScreenState -dDebugPAUSE I put the flag in wrong place: This is working: ".\jre64\bin\java.exe" -Ddebug -Xms1024m -Xmx1024m -Djava.library.path=./ -cp lwjgl.jar;lwjgl_util.jar;./ zombie.gameStates.MainScreenStatePAUSE