diff --git a/xpcom/threads/nsIThreadManager.idl b/xpcom/threads/nsIThreadManager.idl
index 1e4bcfa65470..f0de4a67eaff 100644
--- a/xpcom/threads/nsIThreadManager.idl
+++ b/xpcom/threads/nsIThreadManager.idl
@@ -45,7 +45,7 @@ interface nsIThread;
 /**
  * An interface for creating and locating nsIThread instances.
  */
-[scriptable, uuid(056216f5-8803-46b4-9199-d95bc1f0446f)]
+[scriptable, uuid(487c10bf-0a22-4148-89fa-790d819dd559)]
 interface nsIThreadManager : nsISupports
 {
   /**
@@ -89,4 +89,10 @@ interface nsIThreadManager : nsISupports
    * application process.
    */
   readonly attribute boolean isMainThread;
+
+  /**
+   * This attribute is true if the calling thread is the thread on which the
+   * cycle collector runs.
+   */
+  readonly attribute boolean isCycleCollectorThread;
 };
diff --git a/xpcom/threads/nsThreadManager.cpp b/xpcom/threads/nsThreadManager.cpp
index 0416ef9221c9..7073462843a5 100644
--- a/xpcom/threads/nsThreadManager.cpp
+++ b/xpcom/threads/nsThreadManager.cpp
@@ -305,3 +305,11 @@ nsThreadManager::GetIsMainThread(PRBool *result)
   *result = (PR_GetCurrentThread() == mMainPRThread);
   return NS_OK;
 }
+
+NS_IMETHODIMP
+nsThreadManager::GetIsCycleCollectorThread(PRBool *result)
+{
+  // Not yet implemented.
+  *result = PR_FALSE;
+  return NS_OK;
+}