diff --git a/cmd/minitiad/launch.go b/cmd/minitiad/launch.go
index 9d7368bb..e7545885 100644
--- a/cmd/minitiad/launch.go
+++ b/cmd/minitiad/launch.go
@@ -11,6 +11,7 @@ import (
 	"github.com/initia-labs/OPinit/contrib/launchtools/steps"
 	"github.com/initia-labs/initia/app/params"
 	minitiaapp "github.com/initia-labs/minievm/app"
+	"github.com/initia-labs/minievm/types"
 )
 
 // DefaultLaunchStepFactories is a list of default launch step factories.
@@ -50,6 +51,12 @@ func LaunchCommand(ac *appCreator, enc params.EncodingConfig, mbm module.BasicMa
 	return launchtools.LaunchCmd(
 		ac,
 		func(denom string) map[string]json.RawMessage {
+			// default denom in OPinit is "umin"
+			if denom == "umin" {
+				// convert to "GAS"
+				denom = types.BaseDenom
+			}
+
 			return minitiaapp.NewDefaultGenesisState(enc.Codec, mbm, denom)
 		},
 		DefaultLaunchStepFactories,
diff --git a/types/const.go b/types/const.go
index 001f9d22..c1170c55 100644
--- a/types/const.go
+++ b/types/const.go
@@ -2,5 +2,5 @@ package types
 
 const (
 	// BaseDenom base denom for genesis boot
-	BaseDenom = "umin"
+	BaseDenom = "GAS"
 )
diff --git a/x/evm/keeper/msg_server.go b/x/evm/keeper/msg_server.go
index 019f1cbc..763fd8db 100644
--- a/x/evm/keeper/msg_server.go
+++ b/x/evm/keeper/msg_server.go
@@ -179,6 +179,15 @@ func (ms *msgServerImpl) UpdateParams(ctx context.Context, msg *types.MsgUpdateP
 		return nil, govtypes.ErrInvalidSigner.Wrapf("invalid authority; expected %s, got %s", ms.authority, msg.Authority)
 	}
 
+	params, err := ms.Params.Get(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	if params.FeeDenom != msg.Params.FeeDenom {
+		return nil, sdkerrors.ErrInvalidRequest.Wrap("fee denom cannot be changed")
+	}
+
 	// validate params
 	if err := msg.Params.Validate(ms.ac); err != nil {
 		return nil, err
diff --git a/x/evm/keeper/msg_server_test.go b/x/evm/keeper/msg_server_test.go
index 35b21cc9..3330ba6d 100644
--- a/x/evm/keeper/msg_server_test.go
+++ b/x/evm/keeper/msg_server_test.go
@@ -138,6 +138,15 @@ func Test_MsgServer_UpdateParams(t *testing.T) {
 	})
 	require.Error(t, err)
 
+	// cannot change fee denom
+	params = types.DefaultParams()
+	params.FeeDenom = "otherdenom"
+	_, err = msgServer.UpdateParams(ctx, &types.MsgUpdateParams{
+		Authority: input.EVMKeeper.GetAuthority(),
+		Params:    params,
+	})
+	require.ErrorContains(t, err, "fee denom cannot be changed")
+
 	// valid
 	_, _, addr := keyPubAddr()
 	params = types.DefaultParams()