Hello, I filed a bug report with Gnome about this issue. https://bugzilla.gnome.org/show_bug.cgi?id=752094
They replied that it works just fine with gtk 3.16 and 3.17 with fluxbox 1.3.6, Libgtk3 on Jessie is 3.14.5-1, so maybe this is something that can be updated. Thanks
