diff --git a/src/core/drive/preloader.js b/src/core/drive/preloader.js
index 7deca1857..d23c612a6 100644
--- a/src/core/drive/preloader.js
+++ b/src/core/drive/preloader.js
@@ -43,7 +43,7 @@ export class Preloader {
   // Fetch request delegate
 
   prepareRequest(fetchRequest) {
-    fetchRequest.headers["Sec-Purpose"] = "prefetch"
+    fetchRequest.headers["X-Sec-Purpose"] = "prefetch"
   }
 
   async requestSucceededWithResponse(fetchRequest, fetchResponse) {
diff --git a/src/observers/link_prefetch_observer.js b/src/observers/link_prefetch_observer.js
index d204cb2a5..19a7b9ddd 100644
--- a/src/observers/link_prefetch_observer.js
+++ b/src/observers/link_prefetch_observer.js
@@ -98,7 +98,7 @@ export class LinkPrefetchObserver {
   prepareRequest(request) {
     const link = request.target
 
-    request.headers["Sec-Purpose"] = "prefetch"
+    request.headers["X-Sec-Purpose"] = "prefetch"
 
     const turboFrame = link.closest("turbo-frame")
     const turboFrameTarget = link.getAttribute("data-turbo-frame") || turboFrame?.getAttribute("target") || turboFrame?.id