diff --git a/t/t_rfc4648.c b/t/t_rfc4648.c
index c82c8a0..81c2d23 100644
--- a/t/t_rfc4648.c
+++ b/t/t_rfc4648.c
@@ -34,6 +34,7 @@
 #endif
 
 #include <err.h>
+#include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>