diff --git a/params/protocol_params.go b/params/protocol_params.go
index ae64c46c47..24c6bdd05e 100755
--- a/params/protocol_params.go
+++ b/params/protocol_params.go
@@ -33,7 +33,7 @@ var (
 	DifficultyBoundDivisor = big.NewInt(2048)    // The bound divisor of the difficulty, used in the update calculations.
 	QuadCoeffDiv           = big.NewInt(512)     // Divisor for the quadratic particle of the memory cost equation.
 	GenesisDifficulty      = big.NewInt(131072)  // Difficulty of the Genesis block.
-	DurationLimit          = big.NewInt(8)       // The decision boundary on the blocktime duration used to determine whether difficulty should go up or not.
+	DurationLimit          = big.NewInt(13)      // The decision boundary on the blocktime duration used to determine whether difficulty should go up or not.
 	SstoreSetGas           = big.NewInt(20000)   // Once per SLOAD operation.
 	LogDataGas             = big.NewInt(8)       // Per byte in a LOG* operation's data.
 	CallStipend            = big.NewInt(2300)    // Free gas given at beginning of call.