diff --git a/.changeset/tall-hairs-dream.md b/.changeset/tall-hairs-dream.md
new file mode 100644
index 00000000000..4da8d7924f1
--- /dev/null
+++ b/.changeset/tall-hairs-dream.md
@@ -0,0 +1,5 @@
+---
+"@clerk/remix": patch
+---
+
+Fix issues caused by modifying duplex property on Request when it was already defined
diff --git a/packages/remix/src/ssr/utils.ts b/packages/remix/src/ssr/utils.ts
index 8ee504b4133..d4e8a6f7a14 100644
--- a/packages/remix/src/ssr/utils.ts
+++ b/packages/remix/src/ssr/utils.ts
@@ -126,7 +126,8 @@ export const wrapWithClerkState = (data: any) => {
  */
 export const patchRequest = (request: Request) => {
   const clonedRequest = request.clone();
-  if (clonedRequest.method !== 'GET' && clonedRequest.body !== null) {
+  // If duplex is not set, set it to 'half' to avoid duplex issues with unidici
+  if (clonedRequest.method !== 'GET' && clonedRequest.body !== null && !('duplex' in clonedRequest)) {
     (clonedRequest as unknown as { duplex: 'half' }).duplex = 'half';
   }
   return clonedRequest;