--- a/dom/webidl/AudioContext.webidl
+++ b/dom/webidl/AudioContext.webidl
@@ -5,18 +5,22 @@
  *
  * The origin of this IDL file is
  * https://webaudio.github.io/web-audio-api/
  *
  * Copyright © 2012 W3C® (MIT, ERCIM, Keio), All Rights Reserved. W3C
  * liability, trademark and document use rules apply.
  */
 
-[Constructor,
- Pref="dom.webaudio.enabled"]
+dictionary AudioContextOptions {
+             float        sampleRate = 0;
+};
+
+[Pref="dom.webaudio.enabled",
+ Constructor(optional AudioContextOptions contextOptions)]
 interface AudioContext : BaseAudioContext {
 
     // Bug 1324545: readonly        attribute double outputLatency;
     // Bug 1324545: AudioTimestamp                  getOutputTimestamp ();
 
     [Throws]
     Promise<void> suspend();
     [Throws]