diff --git a/apps/rand.c b/apps/rand.c
index f1c2e9491d..cfbba30755 100644
--- a/apps/rand.c
+++ b/apps/rand.c
@@ -4,6 +4,7 @@
 
 #include <ctype.h>
 #include <stdio.h>
+#include <string.h>
 
 #include <openssl/bio.h>
 #include <openssl/err.h>