diff --git a/cpu/lpc2387/mci/lpc2387-mci.c b/cpu/lpc2387/mci/lpc2387-mci.c
index e61121ece7afe6751ef57eb6f72bee592de245c1..804377fa11f03dfd05aa0a1116e2faf79de6e844 100644
--- a/cpu/lpc2387/mci/lpc2387-mci.c
+++ b/cpu/lpc2387/mci/lpc2387-mci.c
@@ -578,7 +578,8 @@ diskio_sta_t mci_initialize(void)
 
             /* This loop will take a time. Insert wai_tsk(1) here for multitask envilonment. */
             if (xtimer_now_usec() > (start + 1000000/* !Timer[0] */)) {
-                DEBUG("now: %lu, started at: %lu\n", xtimer_now_usec(), start);
+                DEBUG("now: %" PRIu32 ", started at: %" PRIu32 "\n",
+                      xtimer_now_usec(), start);
                 DEBUG("%s, %d: Timeout #2\n", RIOT_FILE_RELATIVE, __LINE__);
                 goto di_fail;
             }