diff --git a/4chan_x.user.js b/4chan_x.user.js
index a8e15dd7c..2b0e0becb 100644
--- a/4chan_x.user.js
+++ b/4chan_x.user.js
@@ -5823,14 +5823,14 @@
       return $.addClass(QR.el, 'dump');
     },
     fileInput: function() {
-      var file, _i, _len, _ref;
+      var file, _i, _len, _ref, _ref1, _ref2;
       QR.cleanNotifications();
       if (this.files.length === 1) {
         file = this.files[0];
         if (file.size > this.max) {
           QR.error("File too large (file: " + ($.bytesToString(file.size)) + ", max: " + ($.bytesToString(this.max)) + ").");
           QR.resetFileInput();
-        } else if (-1 === QR.mimeTypes.indexOf(file.type)) {
+        } else if (_ref = file.type, __indexOf.call(QR.mimeTypes, _ref) < 0) {
           QR.error('Unsupported file type.');
           QR.resetFileInput();
         } else {
@@ -5838,12 +5838,12 @@
         }
         return;
       }
-      _ref = this.files;
-      for (_i = 0, _len = _ref.length; _i < _len; _i++) {
-        file = _ref[_i];
+      _ref1 = this.files;
+      for (_i = 0, _len = _ref1.length; _i < _len; _i++) {
+        file = _ref1[_i];
         if (file.size > this.max) {
           QR.error("File " + file.name + " is too large (file: " + ($.bytesToString(file.size)) + ", max: " + ($.bytesToString(this.max)) + ").");
-        } else if (-1 === QR.mimeTypes.indexOf(file.type)) {
+        } else if (_ref2 = file.type, __indexOf.call(QR.mimeTypes, _ref2) < 0) {
           QR.error("" + file.name + ": Unsupported file type.");
         }
         if (!QR.replies[QR.replies.length - 1].file) {
@@ -6054,7 +6054,7 @@
     captcha: {
       init: function() {
         var _this = this;
-        if (-1 !== d.cookie.indexOf('pass_enabled=')) {
+        if (__indexOf.call(d.cookie, 'pass_enabled=') < 0) {
           return;
         }
         if (!(this.isEnabled = !!$.id('captchaFormPart'))) {
diff --git a/src/qr.coffee b/src/qr.coffee
index f286f8873..065bee66f 100644
--- a/src/qr.coffee
+++ b/src/qr.coffee
@@ -291,7 +291,7 @@ QR =
       if file.size > @max
         QR.error "File too large (file: #{$.bytesToString file.size}, max: #{$.bytesToString @max})."
         QR.resetFileInput()
-      else if -1 is QR.mimeTypes.indexOf file.type
+      else unless file.type in QR.mimeTypes
         QR.error 'Unsupported file type.'
         QR.resetFileInput()
       else
@@ -301,7 +301,7 @@ QR =
     for file in @files
       if file.size > @max
         QR.error "File #{file.name} is too large (file: #{$.bytesToString file.size}, max: #{$.bytesToString @max})."
-      else if -1 is QR.mimeTypes.indexOf file.type
+      else unless file.type in QR.mimeTypes
         QR.error "#{file.name}: Unsupported file type."
       unless QR.replies[QR.replies.length - 1].file
         # set last reply's file
@@ -456,7 +456,7 @@ QR =
 
   captcha:
     init: ->
-      return if -1 isnt d.cookie.indexOf 'pass_enabled='
+      return unless 'pass_enabled=' in d.cookie
       return unless @isEnabled = !!$.id 'captchaFormPart'
       if $.id 'recaptcha_challenge_field_holder'
         @ready()