diff --git a/libdevcrypto/Common.cpp b/libdevcrypto/Common.cpp
index f9720fb8d..089fc7452 100644
--- a/libdevcrypto/Common.cpp
+++ b/libdevcrypto/Common.cpp
@@ -39,7 +39,9 @@ bool dev::SignatureStruct::isValid() const
 {
 	if (v > 1 ||
 		r >= h256("0xfffffffffffffffffffffffffffffffebaaedce6af48a03bbfd25e8cd0364141") ||
-		s >= h256("0xfffffffffffffffffffffffffffffffffffffffffffffffffffffffefffffc2f"))
+		s >= h256("0xfffffffffffffffffffffffffffffffebaaedce6af48a03bbfd25e8cd0364141") ||
+		s < h256("0x01") ||
+		r < h256("0x01"))
 		return false;
 	return true;
 }