diff --git a/core/vm/contracts.go b/core/vm/contracts.go
index 8dd7b9f056..92a4e7d016 100644
--- a/core/vm/contracts.go
+++ b/core/vm/contracts.go
@@ -459,6 +459,8 @@ func (c *bigModExp) RequiredGas(input []byte) uint64 {
 			minPrice = 500
 			if maxLenOver32 {
 				gas.Add(gas, gas)
+			} else {
+				gas = big.NewInt(16)
 			}
 		}