Fix ECDSA sign buffer size
diff --git a/library/ecdsa.c b/library/ecdsa.c
index 5af7f6b..e9880ef 100644
--- a/library/ecdsa.c
+++ b/library/ecdsa.c
@@ -333,7 +333,7 @@
 #if POLARSSL_ECP_MAX_BYTES > 124
 #error "POLARSSL_ECP_MAX_BYTES bigger than expected, please fix MAX_SIG_LEN"
 #endif
-#define MAX_SIG_LEN ( 3 + 2 * ( 2 + POLARSSL_ECP_MAX_BYTES ) )
+#define MAX_SIG_LEN ( 3 + 2 * ( 3 + POLARSSL_ECP_MAX_BYTES ) )
 
 /*
  * Convert a signature (given by context) to ASN.1