diff --git a/cmd/geth/genesis_test.go b/cmd/geth/genesis_test.go
index 7485d7d89..43d678d89 100644
--- a/cmd/geth/genesis_test.go
+++ b/cmd/geth/genesis_test.go
@@ -75,6 +75,7 @@ var customGenesisTests = []struct {
 			"timestamp"  : "0x00",
 			"config"     : {
 				"homesteadBlock" : 314,
+				"daoForkBlock"   : 141
 			},
 		}`,
 		query:  "eth.getBlock(0).nonce",
diff --git a/miner/worker.go b/miner/worker.go
index 09cf6b6aa..7197a33ba 100644
--- a/miner/worker.go
+++ b/miner/worker.go
@@ -33,6 +33,7 @@ import (
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/logger"
 	"github.com/ethereum/go-ethereum/logger/glog"
+	"github.com/ethereum/go-ethereum/params"
 	"github.com/ethereum/go-ethereum/pow"
 	"gopkg.in/fatih/set.v0"
 )
@@ -468,7 +469,14 @@ func (self *worker) commitNewWork() {
 		Extra:      self.extra,
 		Time:       big.NewInt(tstamp),
 	}
-
+	// If we are doing a DAO hard-fork check whether to override the extra-data or not
+	if daoBlock := self.config.DAOForkBlock; daoBlock != nil {
+		// Check whether the block is among the fork extra-override range
+		limit := new(big.Int).Add(daoBlock, params.DAOForkExtraRange)
+		if daoBlock.Cmp(header.Number) <= 0 && header.Number.Cmp(limit) < 0 {
+			header.Extra = common.CopyBytes(params.DAOForkBlockExtra)
+		}
+	}
 	previous := self.current
 	// Could potentially happen if starting to mine in an odd state.
 	err := self.makeCurrent(parent, header)
diff --git a/params/util.go b/params/util.go
index b76850852..a0c9a3199 100644
--- a/params/util.go
+++ b/params/util.go
@@ -16,11 +16,18 @@
 
 package params
 
-import "math/big"
+import (
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/common"
+)
 
 var (
-	TestNetHomesteadBlock = big.NewInt(494000)  // testnet homestead block
-	MainNetHomesteadBlock = big.NewInt(1150000) // mainnet homestead block
-	TestNetDAOForkBlock   = big.NewInt(8888888) // testnet dao hard-fork block
-	MainNetDAOForkBlock   = big.NewInt(9999999) // mainnet dao hard-fork block
+	TestNetHomesteadBlock = big.NewInt(494000)  // Testnet homestead block
+	MainNetHomesteadBlock = big.NewInt(1150000) // Mainnet homestead block
+
+	TestNetDAOForkBlock = big.NewInt(8888888)                            // Testnet dao hard-fork block
+	MainNetDAOForkBlock = big.NewInt(9999999)                            // Mainnet dao hard-fork block
+	DAOForkBlockExtra   = common.FromHex("0x64616f2d686172642d666f726b") // Block extradata to signel the fork with ("dao-hard-fork")
+	DAOForkExtraRange   = big.NewInt(10)                                 // Number of blocks to override the extradata (prevent no-fork attacks)
 )