diff --git a/mozilla/toolkit/mozapps/handling/content/dialog.js b/mozilla/toolkit/mozapps/handling/content/dialog.js
index de4271a17d4..abd1126c056 100644
--- a/mozilla/toolkit/mozapps/handling/content/dialog.js
+++ b/mozilla/toolkit/mozapps/handling/content/dialog.js
@@ -171,17 +171,28 @@ var dialog = {
       let uri = Cc["@mozilla.org/network/util;1"].
                 getService(Ci.nsIIOService).
                 newFileURI(fp.file);
-      let elm = document.createElement("richlistitem");
-      elm.setAttribute("type", "handler");
-      elm.setAttribute("name", fp.file.leafName);
-      elm.setAttribute("image", "moz-icon://" + uri.spec + "?size=32");
 
       let handlerApp = Cc["@mozilla.org/uriloader/local-handler-app;1"].
                        createInstance(Ci.nsILocalHandlerApp);
       handlerApp.executable = fp.file;
+
+      // if this application is already in the list, select it and don't add it again
+      let parent = document.getElementById("items");
+      for (let i = 0; i < parent.childNodes.length; ++i) {
+        let elm = parent.childNodes[i];
+        if (elm.obj instanceof Ci.nsILocalHandlerApp && elm.obj.equals(handlerApp)) {
+          parent.selectedItem = elm;
+          parent.ensureSelectedElementIsVisible();
+          return;
+        }
+      }
+
+      let elm = document.createElement("richlistitem");
+      elm.setAttribute("type", "handler");
+      elm.setAttribute("name", fp.file.leafName);
+      elm.setAttribute("image", "moz-icon://" + uri.spec + "?size=32");
       elm.obj = handlerApp;
 
-      let parent = document.getElementById("items");
       parent.selectedItem = parent.insertBefore(elm, parent.firstChild);
       parent.ensureSelectedElementIsVisible();
     }