diff --git a/src/General/Main.coffee b/src/General/Main.coffee
index a09b9afbb..36ca8436b 100644
--- a/src/General/Main.coffee
+++ b/src/General/Main.coffee
@@ -155,7 +155,7 @@ Main =
       $.addClass doc, style
     setStyle()
     return unless mainStyleSheet
-    if MutationObserver = window.MutationObserver or window.WebKitMutationObserver or window.OMutationObserver
+    if MutationObserver
       observer = new MutationObserver setStyle
       observer.observe mainStyleSheet,
         attributes: true
diff --git a/src/Posting/QR.coffee b/src/Posting/QR.coffee
index f219575ec..1c260737a 100644
--- a/src/Posting/QR.coffee
+++ b/src/Posting/QR.coffee
@@ -703,7 +703,7 @@ QR =
         img:       imgContainer.firstChild
         input:     input
 
-      if MutationObserver = window.MutationObserver or window.WebKitMutationObserver or window.OMutationObserver
+      if MutationObserver
         observer = new MutationObserver @load.bind @
         observer.observe @nodes.challenge,
           childList: true