diff --git a/sys/include/net/nanocoap.h b/sys/include/net/nanocoap.h
index 54dd22c41b98..add6f1c7062d 100644
--- a/sys/include/net/nanocoap.h
+++ b/sys/include/net/nanocoap.h
@@ -2120,7 +2120,7 @@ ssize_t coap_build_hdr(coap_hdr_t *hdr, unsigned type, const void *token,
  * ```
  */
 ssize_t coap_build_reply(coap_pkt_t *pkt, unsigned code,
-                         uint8_t *rbuf, unsigned rlen, unsigned data_len);
+                         uint8_t *rbuf, unsigned rlen, unsigned max_data_len);
 
 /**
  * @brief   Build empty reply to CoAP request