diff --git a/cmd/utils/flags.go b/cmd/utils/flags.go
index cac8773e2..dd18fd78c 100644
--- a/cmd/utils/flags.go
+++ b/cmd/utils/flags.go
@@ -847,61 +847,40 @@ func MakeChainConfigFromDb(ctx *cli.Context, db ethdb.Database) *params.ChainCon
 		(genesis.Hash() == params.MainNetGenesisHash && !ctx.GlobalBool(TestNetFlag.Name)) ||
 		(genesis.Hash() == params.TestNetGenesisHash && ctx.GlobalBool(TestNetFlag.Name))
 
-	// Set any missing chainConfig fields due to them being unset or system upgrade
 	if defaults {
-		if config.HomesteadBlock == nil {
-			if ctx.GlobalBool(TestNetFlag.Name) {
-				config.HomesteadBlock = params.TestNetHomesteadBlock
-			} else {
-				config.HomesteadBlock = params.MainNetHomesteadBlock
-			}
+		// Homestead fork
+		if ctx.GlobalBool(TestNetFlag.Name) {
+			config.HomesteadBlock = params.TestNetHomesteadBlock
+		} else {
+			config.HomesteadBlock = params.MainNetHomesteadBlock
 		}
-		if config.DAOForkBlock == nil {
-			if ctx.GlobalBool(TestNetFlag.Name) {
-				config.DAOForkBlock = params.TestNetDAOForkBlock
-			} else {
-				config.DAOForkBlock = params.MainNetDAOForkBlock
-			}
-			config.DAOForkSupport = true
-		}
-		if config.EIP150Block == nil {
-			if ctx.GlobalBool(TestNetFlag.Name) {
-				config.EIP150Block = params.TestNetHomesteadGasRepriceBlock
-			} else {
-				config.EIP150Block = params.MainNetHomesteadGasRepriceBlock
-			}
-		}
-		if config.EIP150Hash == (common.Hash{}) {
-			if ctx.GlobalBool(TestNetFlag.Name) {
-				config.EIP150Hash = params.TestNetHomesteadGasRepriceHash
-			} else {
-				config.EIP150Hash = params.MainNetHomesteadGasRepriceHash
-			}
-		}
-		if config.EIP155Block == nil {
-			if ctx.GlobalBool(TestNetFlag.Name) {
-				config.EIP150Block = params.TestNetSpuriousDragon
-			} else {
-				config.EIP155Block = params.MainNetSpuriousDragon
-			}
-		}
-		if config.EIP158Block == nil {
-			if ctx.GlobalBool(TestNetFlag.Name) {
-				config.EIP158Block = params.TestNetSpuriousDragon
-			} else {
-				config.EIP158Block = params.MainNetSpuriousDragon
-			}
-		}
-		if config.ChainId.BitLen() == 0 {
-			if ctx.GlobalBool(TestNetFlag.Name) {
-				config.ChainId = params.TestNetChainID
-			} else {
-				config.ChainId = params.MainNetChainID
-			}
+		// DAO fork
+		if ctx.GlobalBool(TestNetFlag.Name) {
+			config.DAOForkBlock = params.TestNetDAOForkBlock
+		} else {
+			config.DAOForkBlock = params.MainNetDAOForkBlock
 		}
 		config.DAOForkSupport = true
-	}
 
+		// DoS reprice fork
+		if ctx.GlobalBool(TestNetFlag.Name) {
+			config.EIP150Block = params.TestNetHomesteadGasRepriceBlock
+			config.EIP150Hash = params.TestNetHomesteadGasRepriceHash
+		} else {
+			config.EIP150Block = params.MainNetHomesteadGasRepriceBlock
+			config.EIP150Hash = params.MainNetHomesteadGasRepriceHash
+		}
+		// DoS state cleanup fork
+		if ctx.GlobalBool(TestNetFlag.Name) {
+			config.EIP155Block = params.TestNetSpuriousDragon
+			config.EIP158Block = params.TestNetSpuriousDragon
+			config.ChainId = params.TestNetChainID
+		} else {
+			config.EIP155Block = params.MainNetSpuriousDragon
+			config.EIP158Block = params.MainNetSpuriousDragon
+			config.ChainId = params.MainNetChainID
+		}
+	}
 	// Force override any existing configs if explicitly requested
 	switch {
 	case ctx.GlobalBool(SupportDAOFork.Name):
diff --git a/mobile/geth.go b/mobile/geth.go
index d7f0800e0..e209b667c 100644
--- a/mobile/geth.go
+++ b/mobile/geth.go
@@ -130,6 +130,7 @@ func NewNode(datadir string, config *NodeConfig) (*Node, error) {
 	if config.EthereumEnabled {
 		ethConf := &eth.Config{
 			ChainConfig: &params.ChainConfig{
+				ChainId:        big.NewInt(config.EthereumChainConfig.ChainID),
 				HomesteadBlock: big.NewInt(config.EthereumChainConfig.HomesteadBlock),
 				DAOForkBlock:   big.NewInt(config.EthereumChainConfig.DAOForkBlock),
 				DAOForkSupport: config.EthereumChainConfig.DAOForkSupport,
diff --git a/mobile/params.go b/mobile/params.go
index 48344a538..1b9f124b4 100644
--- a/mobile/params.go
+++ b/mobile/params.go
@@ -27,6 +27,7 @@ import (
 // MainnetChainConfig returns the chain configurations for the main Ethereum network.
 func MainnetChainConfig() *ChainConfig {
 	return &ChainConfig{
+		ChainID:        params.MainNetChainID.Int64(),
 		HomesteadBlock: params.MainNetHomesteadBlock.Int64(),
 		DAOForkBlock:   params.MainNetDAOForkBlock.Int64(),
 		DAOForkSupport: true,
@@ -46,9 +47,10 @@ func MainnetGenesis() string {
 // TestnetChainConfig returns the chain configurations for the Ethereum test network.
 func TestnetChainConfig() *ChainConfig {
 	return &ChainConfig{
+		ChainID:        params.TestNetChainID.Int64(),
 		HomesteadBlock: params.TestNetHomesteadBlock.Int64(),
 		DAOForkBlock:   0,
-		DAOForkSupport: false,
+		DAOForkSupport: true,
 		EIP150Block:    params.TestNetHomesteadGasRepriceBlock.Int64(),
 		EIP150Hash:     Hash{params.TestNetHomesteadGasRepriceHash},
 		EIP155Block:    params.TestNetSpuriousDragon.Int64(),
@@ -63,6 +65,7 @@ func TestnetGenesis() string {
 
 // ChainConfig is the core config which determines the blockchain settings.
 type ChainConfig struct {
+	ChainID        int64 // Chain ID for replay protection
 	HomesteadBlock int64 // Homestead switch block
 	DAOForkBlock   int64 // TheDAO hard-fork switch block
 	DAOForkSupport bool  // Whether the nodes supports or opposes the DAO hard-fork
diff --git a/params/config.go b/params/config.go
index d27973a32..6d8d73a9b 100644
--- a/params/config.go
+++ b/params/config.go
@@ -24,6 +24,7 @@ import (
 
 // MainnetChainConfig is the chain parameters to run a node on the main network.
 var MainnetChainConfig = &ChainConfig{
+	ChainId:        MainNetChainID,
 	HomesteadBlock: MainNetHomesteadBlock,
 	DAOForkBlock:   MainNetDAOForkBlock,
 	DAOForkSupport: true,
@@ -35,6 +36,7 @@ var MainnetChainConfig = &ChainConfig{
 
 // TestnetChainConfig is the chain parameters to run a node on the test network.
 var TestnetChainConfig = &ChainConfig{
+	ChainId:        TestNetChainID,
 	HomesteadBlock: TestNetHomesteadBlock,
 	DAOForkBlock:   TestNetDAOForkBlock,
 	DAOForkSupport: false,