--- a/js/xpconnect/src/XPCJSRuntime.cpp
+++ b/js/xpconnect/src/XPCJSRuntime.cpp
@@ -210,17 +210,16 @@ public:
 namespace xpc {
 
 CompartmentPrivate::CompartmentPrivate(JS::Compartment* c)
     : wantXrays(false)
     , allowWaivers(true)
     , isWebExtensionContentScript(false)
     , allowCPOWs(false)
     , isContentXBLCompartment(false)
-    , isAddonCompartment(false)
     , universalXPConnectEnabled(false)
     , forcePermissiveCOWs(false)
     , wasNuked(false)
     , mWrappedJSMap(JSObject2WrappedJSMap::newMap(XPC_JS_MAP_LENGTH))
 {
     MOZ_COUNT_CTOR(xpc::CompartmentPrivate);
     mozilla::PodArrayZero(wrapperDenialWarnings);
 }

--- a/js/xpconnect/src/xpcprivate.h
+++ b/js/xpconnect/src/xpcprivate.h
@@ -2868,21 +2868,16 @@ public:
     // to opt into CPOWs. It's necessary for the implementation of
     // RemoteAddonsParent.jsm.
     bool allowCPOWs;
 
     // True if this compartment is a content XBL compartment. Every global in
     // such a compartment is a content XBL scope.
     bool isContentXBLCompartment;
 
-    // True if EnsureAddonCompartment has been called for this compartment.
-    // Note that this is false for extensions that ship with the browser, like
-    // browser/extensions/activity-stream.
-    bool isAddonCompartment;
-
     // This is only ever set during mochitest runs when enablePrivilege is called.
     // It's intended as a temporary stopgap measure until we can finish ripping out
     // enablePrivilege. Once set, this value is never unset (i.e., it doesn't follow
     // the old scoping rules of enablePrivilege).
     //
     // Using it in production is inherently unsafe.
     bool universalXPConnectEnabled;