diff --git a/ChangeLog b/ChangeLog
index a2b440248..b84d888d3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2008-07-13  Thomas Thurman  <tthurman@gnome.org>
+
+        * src/core/display.c (event_callback): meta_display_screen_for_root()
+        can return NULL, so check for that.  Fixes #422242.  Also tidying.
+
 2008-07-13  Elijah Newren  <newren gmail com>
 
         * src/core/workspace.c (meta_workspace_free): Don't attempt to
diff --git a/src/core/display.c b/src/core/display.c
index 613230ff7..d6c44d103 100644
--- a/src/core/display.c
+++ b/src/core/display.c
@@ -1910,11 +1910,13 @@ event_callback (XEvent   *event,
                       meta_event_mode_to_string (event->xfocus.mode),
                       meta_event_detail_to_string (event->xfocus.detail));
         }
-      else if (meta_display_screen_for_root (display,
-                                             event->xany.window) != NULL)
+      else
         {
-          MetaScreen * screen;
-          screen = meta_display_screen_for_root (display, event->xany.window);
+          MetaScreen *screen =
+                meta_display_screen_for_root(display,
+                                             event->xany.window);
+          if (screen == NULL)
+            break;
 
           meta_topic (META_DEBUG_FOCUS,
                       "Focus %s event received on root window 0x%lx "
@@ -1930,17 +1932,24 @@ event_callback (XEvent   *event,
               event->xfocus.detail == NotifyDetailNone)
             {
               meta_topic (META_DEBUG_FOCUS, 
-                          "Focus got set to None, probably due to brain-damage in the X protocol (see bug 125492).  Setting the default focus window.\n");
-
-              meta_workspace_focus_default_window (screen->active_workspace, NULL, meta_display_get_current_time_roundtrip (display));
+                          "Focus got set to None, probably due to "
+                          "brain-damage in the X protocol (see bug "
+                          "125492).  Setting the default focus window.\n");
+              meta_workspace_focus_default_window (screen->active_workspace,
+                                                   NULL,
+                                                   meta_display_get_current_time_roundtrip (display));
             }
           else if (event->type == FocusIn &&
               event->xfocus.mode == NotifyNormal &&
               event->xfocus.detail == NotifyInferior)
             {
               meta_topic (META_DEBUG_FOCUS,
-                          "Focus got set to root window, probably due to gnome-session logout dialog usage (see bug 153220).  Setting the default focus window.\n");
-              meta_workspace_focus_default_window (screen->active_workspace, NULL, meta_display_get_current_time_roundtrip (display));
+                          "Focus got set to root window, probably due to "
+                          "gnome-session logout dialog usage (see bug "
+                          "153220).  Setting the default focus window.\n");
+              meta_workspace_focus_default_window (screen->active_workspace,
+                                                   NULL,
+                                                   meta_display_get_current_time_roundtrip (display));
             }
 
         }