diff --git a/dom/workers/WorkerPrivate.cpp b/dom/workers/WorkerPrivate.cpp
index fba090160935..1b982aac4a6a 100644
--- a/dom/workers/WorkerPrivate.cpp
+++ b/dom/workers/WorkerPrivate.cpp
@@ -1993,6 +1993,14 @@ WorkerLoadInfo::FinalChannelPrincipalIsValid(nsIChannel* aChannel)
 
   return false;
 }
+
+bool
+WorkerLoadInfo::PrincipalIsValid() const
+{
+  return mPrincipal && mPrincipalInfo &&
+         mPrincipalInfo->type() != PrincipalInfo::T__None &&
+         mPrincipalInfo->type() <= PrincipalInfo::T__Last;
+}
 #endif // defined(DEBUG) || !defined(RELEASE_OR_BETA)
 
 bool
@@ -4017,6 +4025,15 @@ WorkerPrivateParent<Derived>::AssertInnerWindowIsCorrect() const
 
 #endif
 
+#if defined(DEBUG) || !defined(RELEASE_OR_BETA)
+template <class Derived>
+bool
+WorkerPrivateParent<Derived>::PrincipalIsValid() const
+{
+  return mLoadInfo.PrincipalIsValid();
+}
+#endif
+
 class PostDebuggerMessageRunnable final : public Runnable
 {
   WorkerDebugger *mDebugger;
@@ -4589,6 +4606,8 @@ WorkerPrivate::Constructor(JSContext* aCx,
 
   worker->EnableDebugger();
 
+  MOZ_DIAGNOSTIC_ASSERT(worker->PrincipalIsValid());
+
   RefPtr<CompileScriptRunnable> compiler =
     new CompileScriptRunnable(worker, aScriptURL);
   if (!compiler->Dispatch()) {
@@ -4858,6 +4877,8 @@ WorkerPrivate::GetLoadInfo(JSContext* aCx, nsPIDOMWindowInner* aWindow,
     NS_ENSURE_SUCCESS(rv, rv);
   }
 
+  MOZ_DIAGNOSTIC_ASSERT(loadInfo.PrincipalIsValid());
+
   aLoadInfo->StealFrom(loadInfo);
   return NS_OK;
 }
diff --git a/dom/workers/WorkerPrivate.h b/dom/workers/WorkerPrivate.h
index b780866b2cc6..8b9198868f5a 100644
--- a/dom/workers/WorkerPrivate.h
+++ b/dom/workers/WorkerPrivate.h
@@ -867,6 +867,11 @@ public:
   AssertInnerWindowIsCorrect() const
   { }
 #endif
+
+#if defined(DEBUG) || !defined(RELEASE_OR_BETA)
+  bool
+  PrincipalIsValid() const;
+#endif
 };
 
 class WorkerDebugger : public nsIWorkerDebugger {
diff --git a/dom/workers/Workers.h b/dom/workers/Workers.h
index 13e7ab69a4b8..66e5b9ecceab 100644
--- a/dom/workers/Workers.h
+++ b/dom/workers/Workers.h
@@ -293,6 +293,9 @@ struct WorkerLoadInfo
 #if defined(DEBUG) || !defined(RELEASE_OR_BETA)
   bool
   FinalChannelPrincipalIsValid(nsIChannel* aChannel);
+
+  bool
+  PrincipalIsValid() const;
 #endif
 
   bool