diff --git a/dom/workers/WorkerPrivate.cpp b/dom/workers/WorkerPrivate.cpp
index c6de6aeaabb0..af627f33d86d 100644
--- a/dom/workers/WorkerPrivate.cpp
+++ b/dom/workers/WorkerPrivate.cpp
@@ -2495,6 +2495,11 @@ already_AddRefed<WorkerPrivate> WorkerPrivate::Constructor(
     return nullptr;
   }
 
+  // From this point on (worker thread has been started) we
+  // must keep ourself alive. We can now only be cleared by
+  // ClearSelfAndParentEventTargetRef().
+  worker->mSelfRef = worker;
+
   worker->EnableDebugger();
 
   MOZ_DIAGNOSTIC_ASSERT(worker->PrincipalIsValid());
@@ -2511,8 +2516,6 @@ already_AddRefed<WorkerPrivate> WorkerPrivate::Constructor(
     return nullptr;
   }
 
-  worker->mSelfRef = worker;
-
   return worker.forget();
 }