How to debug Designer? I get this exception

Ignition 7.8.0 (b2015101414)
Windows 7 64-bit

When I follow the instructions in the SDK manual (online) for debugging the Designer from Eclipse I get this fail. Is something more than launchclient.jar needed in the classpath?

Starting class: com.inductiveautomation.ignition.designer.DesignerStartupHook
java.lang.NoClassDefFoundError: com/incors/plaf/alloy/AlloyTheme
at java.lang.Class.getDeclaredConstructors0(Native Method)
at java.lang.Class.privateGetDeclaredConstructors(
at java.lang.Class.getConstructor0(
at java.lang.Class.newInstance(