diff --git a/content/bookmarks.js b/content/bookmarks.js
index d3832fa6..0cc68505 100644
--- a/content/bookmarks.js
+++ b/content/bookmarks.js
@@ -174,9 +174,13 @@ vimperator.Bookmarks = function () //{{{
 
         isBookmarked: function(url)
         {
-            var uri = ioService.newURI(url, null, null);
-            var count = {};
-            bookmarksService.getBookmarkIdsForURI(uri, count);
+            try
+            {
+                var uri = ioService.newURI(url, null, null);
+                var count = {};
+                bookmarksService.getBookmarkIdsForURI(uri, count);
+            }
+            catch (e) { return false; }
 
             return count.value > 0;
         },
diff --git a/content/commands.js b/content/commands.js
index c1b5cc55..689faab1 100644
--- a/content/commands.js
+++ b/content/commands.js
@@ -737,7 +737,10 @@ vimperator.Commands = function () //{{{
     commandManager.add(new vimperator.Command(["cd", "chd[ir]"],
         function (args)
         {
-            if (!args || vimperator.io.setCurrentDirectory(args))
+            if (!args)
+                args = "~";
+
+            if (vimperator.io.setCurrentDirectory(args))
                 vimperator.echo(vimperator.io.getCurrentDirectory());
         },
         {