diff --git a/mozilla/extensions/irc/js/lib/command-manager.js b/mozilla/extensions/irc/js/lib/command-manager.js
index 200acdd8eb3..f4a5e93b70d 100644
--- a/mozilla/extensions/irc/js/lib/command-manager.js
+++ b/mozilla/extensions/irc/js/lib/command-manager.js
@@ -344,12 +344,12 @@ function cmgr_uninstkey (command)
 CommandManager.prototype.addCommand =
 function cmgr_add (command)
 {
-    if (command.name in this.commands)
+    if (objectContains(this.commands, command.name))
     {
         /* We've already got a command with this name - invoke the history
          * storage so that we can undo this back to its original state.
          */
-        if (!(command.name in this.commandHistory))
+        if (!objectContains(this.commandHistory, command.name))
             this.commandHistory[command.name] = new Array();
         this.commandHistory[command.name].push(this.commands[command.name]);
     }
@@ -371,7 +371,7 @@ CommandManager.prototype.removeCommand =
 function cmgr_remove (command)
 {
     delete this.commands[command.name];
-    if (command.name in this.commandHistory)
+    if (objectContains(this.commandHistory, command.name))
     {
         /* There was a previous command with this name - restore the most
          * recent from the history, returning the command to its former glory.
@@ -393,7 +393,7 @@ function cmgr_remove (command)
 CommandManager.prototype.addHook =
 function cmgr_hook (commandName, func, id, before)
 {
-    if (!ASSERT(commandName in this.commands,
+    if (!ASSERT(objectContains(this.commands, commandName),
                 "Unknown command '" + commandName + "'"))
     {
         return;
@@ -484,11 +484,8 @@ function cmgr_list (partialName, flags)
 
     /* A command named "eval" wouldn't show up in the result of keys() because
      * eval is not-enumerable, even if overwritten, in Mozilla 1.0. */
-    if (("eval" in this.commands) && (typeof this.commands.eval == "object") &&
-        !arrayContains(commandNames, "eval"))
-    {
+    if (objectContains(this.commands, "eval") && !arrayContains(commandNames, "eval"))
         commandNames.push("eval");
-    }
 
     for (var i in commandNames)
     {
diff --git a/mozilla/extensions/irc/js/lib/utils.js b/mozilla/extensions/irc/js/lib/utils.js
index f9817e28ab0..0fc6d116e7c 100644
--- a/mozilla/extensions/irc/js/lib/utils.js
+++ b/mozilla/extensions/irc/js/lib/utils.js
@@ -801,6 +801,11 @@ function arrayRemoveAt (ary, i)
     ary.splice (i, 1);
 }
 
+function objectContains(o, p)
+{
+    return Object.hasOwnProperty.call(o, p);
+}
+
 /* length should be an even number >= 6 */
 function abbreviateWord (str, length)
 {