--- a/dom/webidl/HTMLMediaElement.webidl
+++ b/dom/webidl/HTMLMediaElement.webidl
@@ -106,18 +106,16 @@ partial interface HTMLMediaElement {
   readonly attribute DOMString mozDebugReaderData;
   [Func="HasDebuggerOrTabsPrivilege", NewObject]
   Promise<DOMString> mozRequestDebugInfo();
 
   [Pref="media.test.dumpDebugInfo"]
   void mozDumpDebugInfo();
 
   attribute MediaStream? srcObject;
-  // TODO: remove prefixed version soon (1183495).
-  attribute MediaStream? mozSrcObject;
 
   attribute boolean mozPreservesPitch;
   readonly attribute boolean mozAutoplayEnabled;
 
   // NB: for internal use with the video controls:
   [Func="IsChromeOrXBL"] attribute boolean mozAllowCasting;
   [Func="IsChromeOrXBL"] attribute boolean mozIsCasting;