diff --git a/examples/utility.c b/examples/utility.c
index a16e765433806b8f8d150e9d6792d5436523d3f5..c089450f4321dca20dea003fa7e879e9c7354e37 100644
--- a/examples/utility.c
+++ b/examples/utility.c
@@ -7,7 +7,7 @@
 
 size_t get_user_msg(char * buf, size_t cap) {
 	memset(buf, 0, cap);
-	printf("Insert a msg of max len %d: ", cap);
+	printf("Insert a msg of max len %zu: ", cap);
 	fgets(buf, cap, stdin);
 	for(size_t len = 0; len<cap; len++)
 		if(buf[len]==0 || buf[len]=='\n')