diff --git a/pkg/wakaama/contrib/lwm2m_client.c b/pkg/wakaama/contrib/lwm2m_client.c
index f5aadb2925..cd5c73fdc6 100644
--- a/pkg/wakaama/contrib/lwm2m_client.c
+++ b/pkg/wakaama/contrib/lwm2m_client.c
@@ -176,12 +176,12 @@ static void *_lwm2m_client_run(void *arg)
             lwm2m_client_connection_t *conn = lwm2m_client_connection_find(
                                             _client_data->conn_list, &remote);
             if (conn) {
-                DEBUG("lwm2m_connection_handle_packet(%d)\n", rcv_len);
+                DEBUG("lwm2m_connection_handle_packet(%i)\n", (int)rcv_len);
                 int result = lwm2m_connection_handle_packet(conn, rcv_buf,
                                                             rcv_len,
                                                             _client_data);
                 if (0 != result) {
-                    DEBUG("error handling message %d\n", result);
+                    DEBUG("error handling message %i\n", result);
                 }
             }
             else {
@@ -190,10 +190,10 @@ static void *_lwm2m_client_run(void *arg)
         }
         else if ((rcv_len < 0) &&
                  ((rcv_len != -EAGAIN) && (rcv_len != -ETIMEDOUT))) {
-            DEBUG("Unexpected sock_udp_recv error code %i\n", rcv_len);
+            DEBUG("Unexpected sock_udp_recv error code %i\n", (int)rcv_len);
         }
         else {
-            DEBUG("UDP error code: %d\n", rcv_len);
+            DEBUG("UDP error code: %i\n", (int)rcv_len);
         }
     }
     return NULL;
diff --git a/pkg/wakaama/contrib/lwm2m_client_connection.c b/pkg/wakaama/contrib/lwm2m_client_connection.c
index 4e294ec59c..47965c5748 100644
--- a/pkg/wakaama/contrib/lwm2m_client_connection.c
+++ b/pkg/wakaama/contrib/lwm2m_client_connection.c
@@ -261,7 +261,7 @@ static int _connection_send(lwm2m_client_connection_t *conn, uint8_t *buffer,
     ssize_t sent_bytes = sock_udp_send(&(client_data->sock), buffer,
                                        buffer_size, &(conn->remote));
     if (sent_bytes <= 0) {
-        DEBUG("[_connection_send] Could not send UDP packet: %d\n", sent_bytes);
+        DEBUG("[_connection_send] Could not send UDP packet: %i\n", (int)sent_bytes);
         return -1;
     }
     conn->last_send = lwm2m_gettime();