diff --git a/library/ssl_cookie.c b/library/ssl_cookie.c
index 2f93116..5167e74 100644
--- a/library/ssl_cookie.c
+++ b/library/ssl_cookie.c
@@ -41,6 +41,8 @@
 #define polarssl_free       free
 #endif
 
+#include <string.h>
+
 /* Implementation that should never be optimized out by the compiler */
 static void polarssl_zeroize( void *v, size_t n ) {
     volatile unsigned char *p = v; while( n-- ) *p++ = 0;