System.getProperty("sling.run.modes") not returning value

All,

we're running 5.6.1. I've started CQ by renaming my jar files:

1) cq5-author-4502

2) cq5-publish-4503

I have a servletfilter that checks the runmode you're in using this way:

System.getProperty("sling.run.modes")

However, when I just run the Author from the quickstart jar, this returns null. When I run Author in debug mode it works fine.

When I run Publish from the quickstart.jar it also runs fine (returns publish).

The strange thing is, when I check in the felix console xxx//system/console/status-slingsettings I do see in all cases the correct runmode displayed.

Anyone any idea? Or tips to help debug.