Java 1.7ea: Files.probeContentType(path) returns null

I'm having a bit 开发者_开发问答of a strange problem with an application using the Files.probeContentType(path)-method to test for file type: On both my Ubuntu and Fedora systems, it works fine, but when moved to a RedHat Enterprise server (2.6.18-194.el5 #1 x86_64 x86_64 x86_64 GNU/Linux), it only returns null. I'm using java 7 early access (1.7.0-ea-b84). I have to use this version due to functionality that isn't included in 1.6.

Does anyone have an idea of what might be the problem here?

It looks like it requires GLib.