What version of GTK+ are you using? Can you post the contents of <about:version>? I wasn't able to reproduce this locally with either GTK version 2.24.29 or 3.18.6.
What version of GTK+ are you using? Can you post the contents of <about:version>? I wasn't able to reproduce this locally with either GTK version 2.24.29 or 3.18.6.