diff --git a/chrome/content/vimperator/commands.js b/chrome/content/vimperator/commands.js
index 613b8ccd..ae3d1ac6 100644
--- a/chrome/content/vimperator/commands.js
+++ b/chrome/content/vimperator/commands.js
@@ -486,6 +486,9 @@ function Commands() //{{{
 
     function argToString(arg, color)
     {
+        if (!arg)
+            return "";
+
         try
         {
             // TODO: move to vimperator.eval()?