diff --git a/programs/pkey/dh_genprime.c b/programs/pkey/dh_genprime.c
index 720232f..a06a792 100644
--- a/programs/pkey/dh_genprime.c
+++ b/programs/pkey/dh_genprime.c
@@ -33,6 +33,7 @@
 #endif
 
 #include <stdio.h>
+#include <string.h>
 
 #include "polarssl/bignum.h"
 #include "polarssl/entropy.h"