diff --git a/apps/er-coap-07/er-coap-07.c b/apps/er-coap-07/er-coap-07.c
index 1e3223b2e..55fa4852f 100644
--- a/apps/er-coap-07/er-coap-07.c
+++ b/apps/er-coap-07/er-coap-07.c
@@ -449,6 +449,7 @@ coap_serialize_message(void *packet, uint8_t *buffer)
     PRINTF("Block2 [%lu%s (%u B/blk)]\n", ((coap_packet_t *)packet)->block2_num, ((coap_packet_t *)packet)->block2_more ? "+" : "", ((coap_packet_t *)packet)->block2_size);
 
     uint32_t block = ((coap_packet_t *)packet)->block2_num << 4;
+printf("encode %lu\n", block>>4);
     if (((coap_packet_t *)packet)->block2_more) block |= 0x8;
     block |= 0xF & log_2(((coap_packet_t *)packet)->block2_size/16);