--- a/browser/base/content/nsContextMenu.js
+++ b/browser/base/content/nsContextMenu.js
@@ -730,17 +730,17 @@ nsContextMenu.prototype = {
       else if (this.target instanceof HTMLCanvasElement) {
         this.onCanvas = true;
       }
       else if (this.target instanceof HTMLVideoElement) {
         let mediaURL = this.target.currentSrc || this.target.src;
         if (this.isMediaURLReusable(mediaURL)) {
           this.mediaURL = mediaURL;
         }
-        if (this.target.isEncrypted) {
+        if (this._isProprietaryDRM()) {
           this.onDRMMedia = true;
         }
         // Firefox always creates a HTMLVideoElement when loading an ogg file
         // directly. If the media is actually audio, be smarter and provide a
         // context menu with audio operations.
         if (this.target.readyState >= this.target.HAVE_METADATA &&
             (this.target.videoWidth == 0 || this.target.videoHeight == 0)) {
           this.onAudio = true;
@@ -749,17 +749,17 @@ nsContextMenu.prototype = {
         }
       }
       else if (this.target instanceof HTMLAudioElement) {
         this.onAudio = true;
         let mediaURL = this.target.currentSrc || this.target.src;
         if (this.isMediaURLReusable(mediaURL)) {
           this.mediaURL = mediaURL;
         }
-        if (this.target.isEncrypted) {
+        if (this._isProprietaryDRM()) {
           this.onDRMMedia = true;
         }
       }
       else if (editFlags & (SpellCheckHelper.INPUT | SpellCheckHelper.TEXTAREA)) {
         this.onTextInput = (editFlags & SpellCheckHelper.TEXTINPUT) !== 0;
         this.onNumeric = (editFlags & SpellCheckHelper.NUMERIC) !== 0;
         this.onEditableArea = (editFlags & SpellCheckHelper.EDITABLE) !== 0;
         this.onPassword = (editFlags & SpellCheckHelper.PASSWORD) !== 0;
@@ -963,16 +963,21 @@ nsContextMenu.prototype = {
     }
     if (!editable) {
       return false;
     }
     // Otherwise make sure that nothing in the parent chain disables spellchecking
     return aNode.spellcheck;
   },
 
+  _isProprietaryDRM: function() {
+    return this.target.isEncrypted && this.target.mediaKeys &&
+           this.target.mediaKeys.keySystem != "org.w3.clearkey";
+  },
+
   _openLinkInParameters : function (extra) {
     let params = { charset: gContextMenuContentData.charSet,
                    referrerURI: gContextMenuContentData.documentURIObject,
                    referrerPolicy: gContextMenuContentData.referrerPolicy,
                    noReferrer: this.linkHasNoReferrer };
     for (let p in extra) {
       params[p] = extra[p];
     }