diff --git a/examples/gateway/proxy-car/README.md b/examples/gateway/proxy-car/README.md
index 1a5c891c27..bc5ef9b2b3 100644
--- a/examples/gateway/proxy-car/README.md
+++ b/examples/gateway/proxy-car/README.md
@@ -3,6 +3,8 @@
 This is an example of building a Gateway that uses `application/vnd.ipld.car`
 responses from another gateway acting as a remote Trustless Gateway and IPNS resolver.
 
+**NOTE:** the CAR backend MUST implement [IPIP-0402: Partial CAR Support on Trustless Gateways](https://specs.ipfs.tech/ipips/ipip-0402/)
+
 ## Build
 
 ```bash