diff --git a/js/src/vm/HelperThreads.cpp b/js/src/vm/HelperThreads.cpp
index e1b063085094..a31a8e90b36c 100644
--- a/js/src/vm/HelperThreads.cpp
+++ b/js/src/vm/HelperThreads.cpp
@@ -202,7 +202,8 @@ ParseTask::ParseTask(ExclusiveContext* cx, JSObject* exclusiveContextGlobal, JSC
     alloc(JSRuntime::TEMP_LIFO_ALLOC_PRIMARY_CHUNK_SIZE),
     exclusiveContextGlobal(initCx->runtime(), exclusiveContextGlobal),
     callback(callback), callbackData(callbackData),
-    script(nullptr), sourceObject(nullptr), errors(cx), overRecursed(false)
+    script(initCx->runtime()), sourceObject(initCx->runtime()),
+    errors(cx), overRecursed(false)
 {
 }
 
@@ -1384,7 +1385,7 @@ HelperThread::handleParseWorkload()
                                                task->options, srcBuf,
                                                /* source_ = */ nullptr,
                                                /* extraSct = */ nullptr,
-                                               /* sourceObjectOut = */ &(task->sourceObject));
+                                               /* sourceObjectOut = */ task->sourceObject.address());
     }
 
     // The callback is invoked while we are still off the main thread.
diff --git a/js/src/vm/HelperThreads.h b/js/src/vm/HelperThreads.h
index 10f1471fad48..aae3c152ddfa 100644
--- a/js/src/vm/HelperThreads.h
+++ b/js/src/vm/HelperThreads.h
@@ -479,10 +479,10 @@ struct ParseTask
     // Holds the final script between the invocation of the callback and the
     // point where FinishOffThreadScript is called, which will destroy the
     // ParseTask.
-    JSScript* script;
+    PersistentRootedScript script;
 
     // Holds the ScriptSourceObject generated for the script compilation.
-    ScriptSourceObject* sourceObject;
+    PersistentRooted<ScriptSourceObject*> sourceObject;
 
     // Any errors or warnings produced during compilation. These are reported
     // when finishing the script.