diff --git a/src/gsm/gsm48.c b/src/gsm/gsm48.c
index f69eee2..10e2b80 100644
--- a/src/gsm/gsm48.c
+++ b/src/gsm/gsm48.c
@@ -27,6 +27,7 @@
 #include <stdio.h>
 #include <string.h>
 #include <stdbool.h>
+#include <inttypes.h>
 
 #include <osmocom/core/utils.h>
 #include <osmocom/core/byteswap.h>
@@ -637,7 +638,7 @@
 		/* Table 10.5.4.3, reverse generate_mid_from_tmsi */
 		if (mi_len == GSM48_TMSI_LEN && mi[0] == (0xf0 | GSM_MI_TYPE_TMSI)) {
 			tmsi = osmo_load32be(&mi[1]);
-			return snprintf(string, str_len, "%u", tmsi);
+			return snprintf(string, str_len, "%"PRIu32, tmsi);
 		}
 		break;
 	case GSM_MI_TYPE_IMSI:
diff --git a/src/utils.c b/src/utils.c
index 9e3414b..a1881f0 100644
--- a/src/utils.c
+++ b/src/utils.c
@@ -26,6 +26,7 @@
 #include <stdint.h>
 #include <errno.h>
 #include <stdio.h>
+#include <inttypes.h>
 
 #include <osmocom/core/utils.h>
 #include <osmocom/core/bit64gen.h>
@@ -54,7 +55,7 @@
 	if (str)
 		return str;
 
-	snprintf(namebuf, sizeof(namebuf), "unknown 0x%x", val);
+	snprintf(namebuf, sizeof(namebuf), "unknown 0x%"PRIx32, val);
 	namebuf[sizeof(namebuf) - 1] = '\0';
 	return namebuf;
 }