diff --git a/Cargo.lock b/Cargo.lock
index 6d46aab..7d2b124 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -233,7 +233,7 @@ checksum = "8b3b72a38c9920a29990df12002c4d069a147c8782f0c211f8a01b2df8f42bfd"
 [[package]]
 name = "ckb-bitcoin-spv-prover"
 version = "0.1.0"
-source = "git+https://github.com/ckb-cell/ckb-bitcoin-spv?rev=a13477b#a13477bd12840fc2cd3e606ceea18d52f9c78e9a"
+source = "git+https://github.com/ckb-cell/ckb-bitcoin-spv?rev=bfc71d7#bfc71d7daf17e96f34e8e287f45254e512383330"
 dependencies = [
  "bitcoin",
  "ckb-bitcoin-spv-verifier",
@@ -243,7 +243,7 @@ dependencies = [
 
 [[package]]
 name = "ckb-bitcoin-spv-type-lock"
-version = "0.1.0"
+version = "0.2.0"
 dependencies = [
  "ckb-bitcoin-spv-verifier",
  "ckb-hash",
@@ -253,7 +253,7 @@ dependencies = [
 [[package]]
 name = "ckb-bitcoin-spv-verifier"
 version = "0.1.0"
-source = "git+https://github.com/ckb-cell/ckb-bitcoin-spv?rev=a13477b#a13477bd12840fc2cd3e606ceea18d52f9c78e9a"
+source = "git+https://github.com/ckb-cell/ckb-bitcoin-spv?rev=bfc71d7#bfc71d7daf17e96f34e8e287f45254e512383330"
 dependencies = [
  "bitcoin",
  "bitcoin_hashes",
diff --git a/checksums.txt b/checksums.txt
index 2183e1a..3d25bfd 100644
--- a/checksums.txt
+++ b/checksums.txt
@@ -1,2 +1,2 @@
 6bbea4820329050e1fc65f9c15cab5948b824c73aa3430d7d92b793c53ca66b6  build/release/can-update-without-ownership-lock
-037b7d66cbe8fcea2d13a3da6693e2fc14d6510a075dce20ebb7289647077a5e  build/release/ckb-bitcoin-spv-type-lock
+eaa9e3aeb1205e611078a819e960c33f4934ea49029aab3445a241955e696ee1  build/release/ckb-bitcoin-spv-type-lock
diff --git a/contracts/ckb-bitcoin-spv-type-lock/Cargo.toml b/contracts/ckb-bitcoin-spv-type-lock/Cargo.toml
index 4266a1a..7bd11d6 100644
--- a/contracts/ckb-bitcoin-spv-type-lock/Cargo.toml
+++ b/contracts/ckb-bitcoin-spv-type-lock/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "ckb-bitcoin-spv-type-lock"
-version = "0.1.0"
+version = "0.2.0"
 authors = ["Boyu Yang <yangby@cryptape.com>"]
 edition = "2021"
 license = "MIT"
@@ -15,6 +15,6 @@ ckb-hash = { version = "0.112.1", default-features = false, features = ["ckb-con
 [dependencies.ckb-bitcoin-spv-verifier]
 version = "0.1.0"
 git = "https://github.com/ckb-cell/ckb-bitcoin-spv"
-rev = "a13477b"
+rev = "bfc71d7"
 default-features = false
-features = ["no-std"]
+features = ["no-std"]
\ No newline at end of file
diff --git a/contracts/ckb-bitcoin-spv-type-lock/README.md b/contracts/ckb-bitcoin-spv-type-lock/README.md
index 6c304d7..3fe4a44 100644
--- a/contracts/ckb-bitcoin-spv-type-lock/README.md
+++ b/contracts/ckb-bitcoin-spv-type-lock/README.md
@@ -45,6 +45,17 @@ A Bitcoin SPV instance contains two types of cells: **SPV info cell** and **SPV
       - tip client cell id
   ```
 
+- Flags
+
+  [Flags](https://github.com/ckb-cell/ckb-bitcoin-spv/blob/bfc71d7daf17e96f34e8e287f45254e512383330/verifier/schemas/types.mol#L58) is the last part of `args` and takes up one byte. The highest two bits 
+  are used to indicate different btc chain types. The supported chain types are:
+  
+  - Mainnet
+  - Testnet
+  - Signet
+  
+  see [BTC chain type] for details.
+
 ### Operations
 
 There are 4 kinds of operations in the Bitcoin SPV type script:
@@ -239,3 +250,5 @@ To verify a transaction using the Bitcoin SPV Client cell, follow these steps:
 [Section "Code Locating"]: https://github.com/nervosnetwork/rfcs/blob/v2020.01.15/rfcs/0022-transaction-structure/0022-transaction-structure.md#code-locating
 [CKB RFC 0032]: https://github.com/nervosnetwork/rfcs/blob/dff5235616e5c7aec706326494dce1c54163c4be/rfcs/0032-ckb-vm-version-selection/0032-ckb-vm-version-selection.md#specification
 [CKB RFC 0051]: https://github.com/nervosnetwork/rfcs/blob/dff5235616e5c7aec706326494dce1c54163c4be/rfcs/0051-ckb2023/0051-ckb2023.md#ckb-vm-v2
+
+[btc chain type]: https://github.com/ckb-cell/ckb-bitcoin-spv/blob/bfc71d7daf17e96f34e8e287f45254e512383330/verifier/src/constants.rs#L3
\ No newline at end of file
diff --git a/tests/Cargo.toml b/tests/Cargo.toml
index a3c3a95..fd4959a 100644
--- a/tests/Cargo.toml
+++ b/tests/Cargo.toml
@@ -17,9 +17,9 @@ walkdir = "2.4"
 [dev-dependencies.ckb-bitcoin-spv-prover]
 version = "0.1.0"
 git = "https://github.com/ckb-cell/ckb-bitcoin-spv"
-rev = "a13477b"
+rev = "bfc71d7"
 
 [dev-dependencies.ckb-bitcoin-spv-verifier]
 version = "0.1.0"
 git = "https://github.com/ckb-cell/ckb-bitcoin-spv"
-rev = "a13477b"
+rev = "bfc71d7"