--- FeedConverter.js.orig	2008-04-02 08:50:52.000000000 +0900
+++ FeedConverter.js	2008-04-04 18:34:43.000000000 +0900
@@ -390,7 +390,10 @@ var FeedResultService = {
 
     switch (handler) {
     case "client":
+      const PREF_SELECTED_APP_ARGS = "browser.feeds.handlers.application.args";
+
       var clientApp = prefs.getComplexValue(getPrefAppForType(feedType), Ci.nsILocalFile);
+      var feedhandlerArgs = safeGetCharPref(PREF_SELECTED_APP_ARGS, Ci.nsILocalFile);
 
       // For the benefit of applications that might know how to deal with more
       // URLs than just feeds, send feed: URLs in the following format:
@@ -403,17 +406,24 @@ var FeedResultService = {
           Cc["@mozilla.org/network/io-service;1"].
           getService(Ci.nsIIOService);
       var feedURI = ios.newURI(spec, null, null);
-      if (feedURI.schemeIs("http")) {
+      if (feedURI.schemeIs("http") && !(feedhandlerArgs)) {
         feedURI.scheme = "feed";
         spec = feedURI.spec;
       }
       else
         spec = "feed:" + spec;
 
-      var ss = 
-          Cc["@mozilla.org/browser/shell-service;1"].
-          getService(Ci.nsIShellService);
-      ss.openApplicationWithURI(clientApp, spec);
+      var file = Cc["@mozilla.org/file/local;1"].createInstance(Ci.nsILocalFile);
+      file.initWithPath(clientApp.persistentDescriptor);
+      var process = Cc["@mozilla.org/process/util;1"].createInstance(Ci.nsIProcess);
+      process.init(file);
+
+      if (feedhandlerArgs)
+          var args = [feedhandlerArgs, spec];
+      else
+          var args = [spec];
+
+      process.run(false, args, args.length);
       break;
 
     default: