diff --git a/sys/include/net/nanocoap.h b/sys/include/net/nanocoap.h
index 9158f85578..b469f511bc 100644
--- a/sys/include/net/nanocoap.h
+++ b/sys/include/net/nanocoap.h
@@ -586,6 +586,7 @@ ssize_t coap_opt_get_next(const coap_pkt_t *pkt, coap_optpos_t *opt,
  *
  * @return        length of option; 0 if the option exists but is empty
  * @return        -ENOENT if option not found
+ * @return        -EINVAL if option cannot be parsed
  */
 ssize_t coap_opt_get_opaque(coap_pkt_t *pkt, unsigned opt_num, uint8_t **value);
 /**@}*/
diff --git a/sys/net/application_layer/nanocoap/nanocoap.c b/sys/net/application_layer/nanocoap/nanocoap.c
index df0853c349..904888cf09 100644
--- a/sys/net/application_layer/nanocoap/nanocoap.c
+++ b/sys/net/application_layer/nanocoap/nanocoap.c
@@ -217,6 +217,10 @@ ssize_t coap_opt_get_opaque(coap_pkt_t *pkt, unsigned opt_num, uint8_t **value)
     int len;
 
     *value = _parse_option(pkt, start, &delta, &len);
+    if (!*value) {
+        return -EINVAL;
+    }
+
     return len;
 }