diff --git a/src/calibre/gui_launch.py b/src/calibre/gui_launch.py
index 28ef8eaea3..afe0f33910 100644
--- a/src/calibre/gui_launch.py
+++ b/src/calibre/gui_launch.py
@@ -41,17 +41,33 @@ def init_dbus():
         threads_init()
         DBusGMainLoop(set_as_default=True)
 
+def register_with_default_programs():
+    from calibre.constants import iswindows
+    if iswindows:
+        from calibre.utils.winreg.default_programs import Register
+        from calibre.gui2 import gprefs
+        return Register(gprefs)
+    else:
+        class Dummy(object):
+            def __enter__(self):
+                return self
+            def __exit__(self, *args):
+                pass
+        return Dummy()
+
 def calibre(args=sys.argv):
     detach_gui()
     init_dbus()
-    from calibre.gui2.main import main
-    main(args)
+    with register_with_default_programs():
+        from calibre.gui2.main import main
+        main(args)
 
 def ebook_viewer(args=sys.argv):
     detach_gui()
     init_dbus()
-    from calibre.gui2.viewer.main import main
-    main(args)
+    with register_with_default_programs():
+        from calibre.gui2.viewer.main import main
+        main(args)
 
 def gui_ebook_edit(path=None, notify=None):
     ' For launching the editor from inside calibre '
@@ -62,8 +78,9 @@ def gui_ebook_edit(path=None, notify=None):
 def ebook_edit(args=sys.argv):
     detach_gui()
     init_dbus()
-    from calibre.gui2.tweak_book.main import main
-    main(args)
+    with register_with_default_programs():
+        from calibre.gui2.tweak_book.main import main
+        main(args)
 
 def option_parser(basename):
     if basename == 'calibre':
diff --git a/src/calibre/utils/winreg/default_programs.py b/src/calibre/utils/winreg/default_programs.py
index f5dbb3087e..49d1d482e8 100644
--- a/src/calibre/utils/winreg/default_programs.py
+++ b/src/calibre/utils/winreg/default_programs.py
@@ -6,7 +6,7 @@ from __future__ import (unicode_literals, division, absolute_import,
 __license__ = 'GPL v3'
 __copyright__ = '2015, Kovid Goyal <kovid at kovidgoyal.net>'
 
-import os, sys
+import os, sys, time
 from threading import Thread
 
 from calibre import guess_type, prints
@@ -157,5 +157,16 @@ class Register(Thread):
             if self.prefs.get('windows_register_default_programs', None) != __version__:
                 self.prefs['windows_register_default_programs'] = __version__
                 if DEBUG:
+                    st = time.time()
                     prints('Registering with default programs...')
                 register()
+                if DEBUG:
+                    prints('Registered with default programs in %.1f seconds' % (time.time() - st))
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, *args):
+        # Give the thread some time to finish in case the user quit the
+        # application very quickly
+        self.join(4.0)