diff --git a/programs/pkey/rsa_genkey.c b/programs/pkey/rsa_genkey.c
index ff31598..56d3273 100644
--- a/programs/pkey/rsa_genkey.c
+++ b/programs/pkey/rsa_genkey.c
@@ -33,6 +33,7 @@
 #endif
 
 #include <stdio.h>
+#include <string.h>
 
 #include "polarssl/entropy.h"
 #include "polarssl/ctr_drbg.h"