diff --git a/apps/rest-coap/coap-server.c b/apps/rest-coap/coap-server.c
index 62ff76870..2fb944325 100644
--- a/apps/rest-coap/coap-server.c
+++ b/apps/rest-coap/coap-server.c
@@ -422,7 +422,7 @@ handle_incoming_data(void)
 
   PRINTF("uip_datalen received %u \n",(u16_t)uip_datalen());
 
-  char* data = uip_appdata + uip_ext_len;
+  char* data = (char *)uip_appdata + uip_ext_len;
   u16_t datalen = uip_datalen() - uip_ext_len;
 
   int data_size = 0;