diff --git a/dom/fetch/FetchParent.cpp b/dom/fetch/FetchParent.cpp
index a36b784e278..5274d6ca9f8 100644
--- a/dom/fetch/FetchParent.cpp
+++ b/dom/fetch/FetchParent.cpp
@@ -136,6 +136,13 @@ IPCResult FetchParent::RecvFetchOp(FetchOpArgs&& aArgs) {
                     "RecvFetchOp FORCE_ALLOWED_DTD not allowed from content");
   }
 
+  if (contentHandle && InternalRequest::IsNavigationContentPolicy(
+                           aArgs.request().contentPolicyType())) {
+    return IPC_FAIL(this,
+                    "RecvFetchOp navigation content policy type not allowed "
+                    "from content");
+  }
+
   mRequest = MakeSafeRefPtr<InternalRequest>(std::move(aArgs.request()));
   mIsWorkerFetch = aArgs.isWorkerRequest();
   mPrincipalInfo = std::move(aArgs.principalInfo());
diff --git a/dom/fetch/InternalRequest.h b/dom/fetch/InternalRequest.h
index 1d0891f77e2..34369d1835e 100644
--- a/dom/fetch/InternalRequest.h
+++ b/dom/fetch/InternalRequest.h
@@ -450,9 +450,11 @@ class InternalRequest final : public AtomicSafeRefCounted<InternalRequest> {
   static RequestDestination MapContentPolicyTypeToRequestDestination(
       ExtContentPolicyType aContentPolicyType);
 
- private:
+  // True for content policy types that are only ever legitimately used for
+  // nsDocShell-initiated navigations, never for a fetch() call.
   static bool IsNavigationContentPolicy(nsContentPolicyType aContentPolicyType);
 
+ private:
   static bool IsWorkerContentPolicy(nsContentPolicyType aContentPolicyType);
 
   // It should only be called while there is a service-worker-internal-redirect.