diff -up ./catfish/__init__.py.0000 ./catfish/__init__.py
--- ./catfish/__init__.py.0000	2014-02-11 17:32:05.427249877 +0200
+++ ./catfish/__init__.py	2014-02-11 17:32:59.069095991 +0200
@@ -20,6 +20,8 @@ import optparse
 
 from locale import gettext as _
 
+import gi
+gi.require_version("Gtk", "3.0")
 from gi.repository import Gtk  # pylint: disable=E0611
 
 from catfish import CatfishWindow
diff -up ./catfish_lib/helpers.py.orig ./catfish_lib/helpers.py
--- ./catfish_lib/helpers.py.orig	2017-03-25 17:46:41.126227294 +0200
+++ ./catfish_lib/helpers.py	2017-03-25 17:47:42.285902864 +0200
@@ -20,6 +20,9 @@
 import logging
 import os
 import sys
+
+import gi
+gi.require_version('Gtk', '3.0')
 from gi.repository import Gtk, GObject
 
 from . catfishconfig import get_data_file