--- a/js/xpconnect/src/Sandbox.cpp
+++ b/js/xpconnect/src/Sandbox.cpp
@@ -989,16 +989,19 @@ xpc::CreateSandboxObject(JSContext* cx, 
         }
     }
     MOZ_ASSERT(principal);
 
     JS::CompartmentOptions compartmentOptions;
 
     auto& creationOptions = compartmentOptions.creationOptions();
 
+    if (xpc::SharedMemoryEnabled())
+        creationOptions.setSharedMemoryAndAtomicsEnabled(true);
+
     if (options.sameZoneAs)
         creationOptions.setSameZoneAs(js::UncheckedUnwrap(options.sameZoneAs));
     else if (options.freshZone)
         creationOptions.setZone(JS::FreshZone);
     else
         creationOptions.setZone(JS::SystemZone);
 
     creationOptions.setInvisibleToDebugger(options.invisibleToDebugger)

--- a/js/xpconnect/src/XPCWrappedNative.cpp
+++ b/js/xpconnect/src/XPCWrappedNative.cpp
@@ -178,16 +178,18 @@ XPCWrappedNative::WrapNewGlobal(xpcObjec
     MOZ_ASSERT(si.get());
 
     // Finally, we get to the JSClass.
     const JSClass* clasp = si->GetJSClass();
     MOZ_ASSERT(clasp->flags & JSCLASS_IS_GLOBAL);
 
     // Create the global.
     aOptions.creationOptions().setTrace(XPCWrappedNative::Trace);
+    if (xpc::SharedMemoryEnabled())
+        aOptions.creationOptions().setSharedMemoryAndAtomicsEnabled(true);
     RootedObject global(cx, xpc::CreateGlobalObject(cx, clasp, principal, aOptions));
     if (!global)
         return NS_ERROR_FAILURE;
     XPCWrappedNativeScope* scope = CompartmentPrivate::Get(global)->scope;
 
     // Immediately enter the global's compartment, so that everything else we
     // create ends up there.
     JSAutoCompartment ac(cx, global);