diff --git a/library/ecdsa.c b/library/ecdsa.c
index 5b62939..60dd427 100644
--- a/library/ecdsa.c
+++ b/library/ecdsa.c
@@ -37,6 +37,8 @@
 #include "polarssl/ecdsa.h"
 #include "polarssl/asn1write.h"
 
+#include <string.h>
+
 #if defined(POLARSSL_ECDSA_DETERMINISTIC)
 #include "polarssl/hmac_drbg.h"
 #endif