diff --git a/core/chain_util.go b/core/chain_util.go
index 6ce13af541..680355e5b7 100644
--- a/core/chain_util.go
+++ b/core/chain_util.go
@@ -40,11 +40,12 @@ var (
 // given the parent block's time and difficulty.
 func CalcDifficulty(time, parentTime uint64, parentNumber, parentDiff *big.Int) *big.Int {
 	diff := new(big.Int)
+    adjust := new(big.Int)
 
 	if parentNumber.Cmp(params.HardFork1) < 0 {
-	    adjust := new(big.Int).Div(parentDiff, params.DifficultyBoundDivisor)
+	    adjust = new(big.Int).Div(parentDiff, params.DifficultyBoundDivisor)
 	} else {
-	    adjust := new(big.Int).Div(parentDiff, params.DifficultyBoundDivisor2)
+	    adjust = new(big.Int).Div(parentDiff, params.DifficultyBoundDivisor2)
 	}
 
 	bigTime := new(big.Int)