diff --git a/common/content/commands.js b/common/content/commands.js
index 4593cd1c..be57f958 100644
--- a/common/content/commands.js
+++ b/common/content/commands.js
@@ -760,7 +760,7 @@ const Commands = Module("commands", {
             function matchOpts(arg) {
                 // Push possible option matches into completions
                 if (complete && !onlyArgumentsRemaining)
-                    completeOpts = options.filter(function (opt) opt.multiple || !(opt.names[0] in args));
+                    completeOpts = options.filter(function (opt) opt.multiple || !set.has(args, opt.names[0]));
             }
             function resetCompletions() {
                 completeOpts = null;
diff --git a/common/content/events.js b/common/content/events.js
index dedaaa21..821ff08f 100644
--- a/common/content/events.js
+++ b/common/content/events.js
@@ -364,6 +364,7 @@ const Events = Module("events", {
                 if (target instanceof Document)
                     target = target.documentElement;
                 dactyl.assert(target);
+
                 // This causes a crash on Gecko<2.0, it seems.
                 target.ownerDocument.defaultView
                       .QueryInterface(Ci.nsIInterfaceRequestor).getInterface(Ci.nsIDOMWindowUtils)