diff --git a/testing/getprime/getprime_main.c b/testing/getprime/getprime_main.c
index 118c78e9c..b4342e95b 100644
--- a/testing/getprime/getprime_main.c
+++ b/testing/getprime/getprime_main.c
@@ -178,6 +178,6 @@ int main(int argc, FAR char *argv[])
   elapsed -= (((uint64_t)ts0.tv_sec * NSEC_PER_SEC) + ts0.tv_nsec);
   elapsed /= NSEC_PER_MSEC; /* msec */
 
-  printf("%s took %ld msec \n", argv[0], elapsed);
+  printf("%s took %" PRIu64 " msec \n", argv[0], elapsed);
   return 0;
 }