diff --git a/sys/include/net/coap.h b/sys/include/net/coap.h
index 358ebf7a07..7e83216e7e 100644
--- a/sys/include/net/coap.h
+++ b/sys/include/net/coap.h
@@ -535,6 +535,11 @@ typedef enum {
 #define COAP_ETAG_LENGTH_MAX     (8U)   /**< maximum length of the ETag option */
 /** @} */
 
+/**
+ * @brief   Marks the boundary between header and payload
+ */
+#define COAP_PAYLOAD_MARKER      (0xFF)
+
 /**
  * @defgroup net_coap_conf    CoAP compile configurations
  * @ingroup  net_coap