diff --git a/library/ecdsa.c b/library/ecdsa.c
index 7f259e1..640eb24 100644
--- a/library/ecdsa.c
+++ b/library/ecdsa.c
@@ -726,7 +726,7 @@
                                     unsigned char *sig, size_t *slen )
 {
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
-    unsigned char buf[MBEDTLS_ECDSA_MAX_LEN];
+    unsigned char buf[MBEDTLS_ECDSA_MAX_LEN] = {0};
     unsigned char *p = buf + sizeof( buf );
     size_t len = 0;