diff --git a/IPython/terminal/pt_inputhooks/gtk.py b/IPython/terminal/pt_inputhooks/gtk.py
index 3360048..8f27e12 100644
--- a/IPython/terminal/pt_inputhooks/gtk.py
+++ b/IPython/terminal/pt_inputhooks/gtk.py
@@ -39,6 +39,9 @@ from __future__ import absolute_import
 
 import gtk, gobject
 
+# Enable threading in GTK. (Otherwise, GTK will keep the GIL.)
+gtk.gdk.threads_init()
+
 def inputhook(context):
     """
     When the eventloop of prompt-toolkit is idle, call this inputhook.