--- a/dom/serviceworkers/test/test_serviceworker_interfaces.js
+++ b/dom/serviceworkers/test/test_serviceworker_interfaces.js
@@ -124,18 +124,16 @@ var interfaceNamesInGlobalScope =
     "FetchEvent",
 // IMPORTANT: Do not change this list without review from a DOM peer!
     "File",
 // IMPORTANT: Do not change this list without review from a DOM peer!
     "FileList",
 // IMPORTANT: Do not change this list without review from a DOM peer!
     "FileReader",
 // IMPORTANT: Do not change this list without review from a DOM peer!
-    "FileReaderSync",
-// IMPORTANT: Do not change this list without review from a DOM peer!
     "FormData",
 // IMPORTANT: Do not change this list without review from a DOM peer!
     "Headers",
 // IMPORTANT: Do not change this list without review from a DOM peer!
     "IDBCursor",
 // IMPORTANT: Do not change this list without review from a DOM peer!
     "IDBCursorWithValue",
 // IMPORTANT: Do not change this list without review from a DOM peer!

--- a/dom/webidl/FileReaderSync.webidl
+++ b/dom/webidl/FileReaderSync.webidl
@@ -6,17 +6,17 @@
  * The origin of this IDL file is
  * http://dev.w3.org/2006/webapi/FileAPI/
  *
  * Copyright © 2012 W3C® (MIT, ERCIM, Keio), All Rights Reserved. W3C
  * liability, trademark and document use rules apply.
  */
 
 [Constructor,
- Exposed=Worker]
+ Exposed=(DedicatedWorker,SharedWorker)]
 interface FileReaderSync {
 
   // Synchronously return strings
 
   [Throws]
   ArrayBuffer readAsArrayBuffer(Blob blob);
   [Throws]
   DOMString readAsBinaryString(Blob blob);

deleted file mode 100644
--- a/testing/web-platform/meta/FileAPI/historical.https.html.ini
+++ /dev/null
@@ -1,4 +0,0 @@
-[historical.https.html]
-  ["FileReaderSync" should not be supported in service workers]
-    expected: FAIL
-