diff --git a/token-erc-20/chaincode-go/chaincode/token_contract.go b/token-erc-20/chaincode-go/chaincode/token_contract.go
index b6b7bad6..9752fd3c 100644
--- a/token-erc-20/chaincode-go/chaincode/token_contract.go
+++ b/token-erc-20/chaincode-go/chaincode/token_contract.go
@@ -723,7 +723,7 @@ func sub(b int, q int) (int, error) {
 	var diff int
 	diff = b - q
 
-	if (diff > b) == (b >= 0 && q >= 0) {
+	if (diff < b || diff < -q) == (b >= 0 && q <= 0) {
 		return 0, fmt.Errorf("Math: Subtraction overflow occurred  %d - %d", b, q)
 	}