diff --git a/usr.sbin/pkg/rsa.c b/usr.sbin/pkg/rsa.c
index b28f44ec195..0056ccb595a 100644
--- a/usr.sbin/pkg/rsa.c
+++ b/usr.sbin/pkg/rsa.c
@@ -32,6 +32,7 @@
 
 #include <err.h>
 #include <stdbool.h>
+#include <string.h>
 
 #include <openssl/err.h>
 #include <openssl/ssl.h>