diff --git a/Cargo.lock b/Cargo.lock
index 1deeed1..7662efa 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -394,7 +394,7 @@ dependencies = [
 
 [[package]]
 name = "ckb-system-scripts"
-version = "0.4.0-alpha.14+2-phase-dao"
+version = "0.4.0-alpha.17+multisig-since"
 dependencies = [
  "blake2b-rs 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "byteorder 1.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
diff --git a/Cargo.toml b/Cargo.toml
index 3cb228b..88d83a6 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "ckb-system-scripts"
-version = "0.4.0-alpha.14+2-phase-dao"
+version = "0.4.0-alpha.17+multisig-since"
 authors = ["Nervos Core Dev <dev@nervos.org>"]
 edition = "2018"
 build = "build.rs"
diff --git a/build.rs b/build.rs
index 14482da..8aac304 100644
--- a/build.rs
+++ b/build.rs
@@ -27,7 +27,7 @@ const BINARIES: &[(&str, &str)] = &[
     ),
     (
         "secp256k1_blake160_multisig_all",
-        "2a450c65ed903e7064a53f95a660bce48a9c94ca64f395c82d5e86884ee25195",
+        "109805c7dc63086bdbbd81efb1c95a5ba2c81baf91a5f3e2564c7c23c5e77264",
     ),
 ];
 
diff --git a/c/secp256k1_blake160_multisig_all.c b/c/secp256k1_blake160_multisig_all.c
index 24317d0..8f58159 100644
--- a/c/secp256k1_blake160_multisig_all.c
+++ b/c/secp256k1_blake160_multisig_all.c
@@ -5,6 +5,7 @@
 #include "secp256k1_helper.h"
 
 /* script args errors */
+#define ERROR_INVALID_RESERVE_FIELD -41
 #define ERROR_INVALID_PUBKEYS_CNT -42
 #define ERROR_INVALID_THRESHOLD -43
 #define ERROR_INVALID_REQUIRE_FIRST_N -44
@@ -22,24 +23,24 @@
 #define MAX_WITNESS_SIZE 32768
 #define MAX_SCRIPT_SIZE 32768
 #define SIGNATURE_SIZE 65
-#define FLAGS_SIZE 12
+#define FLAGS_SIZE 4
 
 /*
  * Arguments:
- * multisig script blake160 hash, 20 bytes.
+ * 1. multisig script blake160 hash, 20 bytes.
+ * 2. an optional since constraint, 4 bytes.
  *
  * Witness:
  * multisig_script | Signature1 | signature2 | ...
- * multisig_script: S | R | M | N | since | Pubkey1 | Pubkey2 | ...
+ * multisig_script: S | R | M | N | Pubkey1 | Pubkey2 | ...
  *
  * +------------+----------------------------------+-------+
  * |            |           Description            | Bytes |
  * +------------+----------------------------------+-------+
- * | S          | reserved for future use          |     1 |
+ * | S          | reserved field, must be zero     |     1 |
  * | R          | first nth public keys must match |     1 |
  * | M          | threshold                        |     1 |
  * | N          | total public keys                |     1 |
- * | since      | tx since verify                  |     8 |
  * | PubkeyN    | compressed pubkey                |    33 |
  * | SignatureN | recoverable signature            |    65 |
  * +------------+----------------------------------+-------+
@@ -68,9 +69,14 @@ int main() {
 
   mol_seg_t args_seg = MolReader_Script_get_args(&script_seg);
   mol_seg_t args_bytes_seg = MolReader_Bytes_raw_bytes(&args_seg);
-  if (args_bytes_seg.size != BLAKE160_SIZE) {
+  if (args_bytes_seg.size != BLAKE160_SIZE &&
+      args_bytes_seg.size != BLAKE160_SIZE + sizeof(uint64_t)) {
     return ERROR_ARGUMENTS_LEN;
   }
+  uint64_t since = 0;
+  if (args_bytes_seg.size == BLAKE160_SIZE + sizeof(uint64_t)) {
+    since = *(uint64_t *)&args_bytes_seg.ptr[BLAKE160_SIZE];
+  }
 
   /* Load witness of first input */
   unsigned char witness[MAX_WITNESS_SIZE];
@@ -97,7 +103,10 @@ int main() {
   uint8_t pubkeys_cnt = lock_bytes[3];
   uint8_t threshold = lock_bytes[2];
   uint8_t require_first_n = lock_bytes[1];
-  uint64_t since = *(uint64_t *)&lock_bytes[4];
+  uint8_t reserved_field = lock_bytes[0];
+  if (reserved_field != 0) {
+    return ERROR_INVALID_RESERVE_FIELD;
+  }
   if (pubkeys_cnt == 0) {
     return ERROR_INVALID_PUBKEYS_CNT;
   }
diff --git a/src/tests/secp256k1_blake160_multisig_all.rs b/src/tests/secp256k1_blake160_multisig_all.rs
index 16d5676..f7bed67 100644
--- a/src/tests/secp256k1_blake160_multisig_all.rs
+++ b/src/tests/secp256k1_blake160_multisig_all.rs
@@ -28,11 +28,11 @@ const ERROR_INCORRECT_SINCE: i8 = -53;
 fn test_multisig_script_hash() {
     let mut data_loader = DummyDataLoader::new();
     let keys = generate_keys(3);
-    let multi_sign_script = gen_multi_sign_script(&keys, 2, 0, 0);
+    let multi_sign_script = gen_multi_sign_script(&keys, 2, 0);
     let args = blake160(&multi_sign_script);
     let raw_tx = gen_tx(&mut data_loader, args);
     {
-        let wrong_multi_sign_script = gen_multi_sign_script(&keys, 2, 1, 0);
+        let wrong_multi_sign_script = gen_multi_sign_script(&keys, 2, 1);
         let tx = multi_sign_tx(
             raw_tx.clone(),
             &wrong_multi_sign_script,
@@ -50,11 +50,11 @@ fn test_multisig_script_hash() {
 fn test_invalid_flags() {
     let mut data_loader = DummyDataLoader::new();
     let keys = generate_keys(3);
-    let multi_sign_script = gen_multi_sign_script(&keys, 2, 0, 0);
+    let multi_sign_script = gen_multi_sign_script(&keys, 2, 0);
     let args = blake160(&multi_sign_script);
     let raw_tx = gen_tx(&mut data_loader, args);
     {
-        let wrong_multi_sign_script = gen_multi_sign_script(&vec![], 2, 0, 0);
+        let wrong_multi_sign_script = gen_multi_sign_script(&vec![], 2, 0);
         let tx = multi_sign_tx(
             raw_tx.clone(),
             &wrong_multi_sign_script,
@@ -67,7 +67,7 @@ fn test_invalid_flags() {
         );
     }
     {
-        let wrong_multi_sign_script = gen_multi_sign_script(&keys, 4, 0, 0);
+        let wrong_multi_sign_script = gen_multi_sign_script(&keys, 4, 0);
         let tx = multi_sign_tx(
             raw_tx.clone(),
             &wrong_multi_sign_script,
@@ -80,7 +80,7 @@ fn test_invalid_flags() {
         );
     }
     {
-        let wrong_multi_sign_script = gen_multi_sign_script(&keys, 2, 3, 0);
+        let wrong_multi_sign_script = gen_multi_sign_script(&keys, 2, 3);
         let tx = multi_sign_tx(
             raw_tx.clone(),
             &wrong_multi_sign_script,
@@ -98,7 +98,7 @@ fn test_invalid_flags() {
 fn test_multisig_0_2_3_unlock() {
     let mut data_loader = DummyDataLoader::new();
     let keys = generate_keys(3);
-    let multi_sign_script = gen_multi_sign_script(&keys, 2, 0, 0);
+    let multi_sign_script = gen_multi_sign_script(&keys, 2, 0);
     let args = blake160(&multi_sign_script);
     let raw_tx = gen_tx(&mut data_loader, args);
     {
@@ -170,7 +170,7 @@ fn test_multisig_0_2_3_unlock() {
 fn test_multisig_1_2_3_unlock() {
     let mut data_loader = DummyDataLoader::new();
     let keys = generate_keys(3);
-    let multi_sign_script = gen_multi_sign_script(&keys, 2, 1, 0);
+    let multi_sign_script = gen_multi_sign_script(&keys, 2, 1);
     let args = blake160(&multi_sign_script);
     let tx = gen_tx(&mut data_loader, args);
     {
@@ -199,7 +199,7 @@ fn test_multisig_1_2_3_unlock() {
 fn test_multisig_1_2_3_with_extra_witness_unlock() {
     let mut data_loader = DummyDataLoader::new();
     let keys = generate_keys(3);
-    let multi_sign_script = gen_multi_sign_script(&keys, 2, 1, 0);
+    let multi_sign_script = gen_multi_sign_script(&keys, 2, 1);
     let args = blake160(&multi_sign_script);
     let tx = gen_tx(&mut data_loader, args);
     let extract_witness = vec![1, 2, 3, 4];
@@ -237,10 +237,9 @@ fn test_multisig_1_2_3_with_extra_witness_unlock() {
 fn test_multisig_1_2_3_with_multiple_inputs_unlock() {
     let mut data_loader = DummyDataLoader::new();
     let keys = generate_keys(3);
-    let multi_sign_script = gen_multi_sign_script(&keys, 2, 1, 0);
+    let multi_sign_script = gen_multi_sign_script(&keys, 2, 1);
     let args = blake160(&multi_sign_script);
     let tx = gen_tx_with_extra_inputs(&mut data_loader, args, 1);
-    dbg!(format!("{}", &tx));
     {
         let tx = multi_sign_tx(tx.clone(), &multi_sign_script, &[&keys[0], &keys[1]]);
         verify(&data_loader, &tx).expect("pass verification");
@@ -267,7 +266,7 @@ fn test_multisig_1_2_3_with_multiple_inputs_unlock() {
 fn test_multisig_0_1_1_unlock() {
     let mut data_loader = DummyDataLoader::new();
     let keys = generate_keys(1);
-    let multi_sign_script = gen_multi_sign_script(&keys, 1, 0, 0);
+    let multi_sign_script = gen_multi_sign_script(&keys, 1, 0);
     let args = blake160(&multi_sign_script);
     let raw_tx = gen_tx(&mut data_loader, args);
     {
@@ -289,7 +288,7 @@ fn test_multisig_0_1_1_unlock() {
 fn test_multisig_0_2_2_unlock() {
     let mut data_loader = DummyDataLoader::new();
     let keys = generate_keys(2);
-    let multi_sign_script = gen_multi_sign_script(&keys, 2, 0, 0);
+    let multi_sign_script = gen_multi_sign_script(&keys, 2, 0);
     let args = blake160(&multi_sign_script);
     let raw_tx = gen_tx(&mut data_loader, args);
     {
@@ -378,22 +377,16 @@ fn test_multisig_0_2_3_unlock_with_since() {
     let mut data_loader = DummyDataLoader::new();
     let keys = generate_keys(3);
     let since = 0x0000_0000_8888_8888u64;
-    let multi_sign_script = gen_multi_sign_script(&keys, 2, 0, since);
-    let args = blake160(&multi_sign_script);
+    let multi_sign_script = gen_multi_sign_script(&keys, 2, 0);
+    let args = {
+        let mut buf = blake160(&multi_sign_script).to_vec();
+        buf.extend(since.to_le_bytes().into_iter());
+        Bytes::from(buf)
+    };
     let raw_tx = gen_tx(&mut data_loader, args);
     {
-        let since2 = 0;
-        let multi_sign_script = gen_multi_sign_script(&keys, 2, 0, since2);
         let tx = multi_sign_tx(raw_tx.clone(), &multi_sign_script, &[&keys[0], &keys[1]]);
         let verify_result = verify(&data_loader, &tx);
-        assert_error_eq!(
-            verify_result.unwrap_err(),
-            ScriptError::ValidationFailure(ERROR_MULTSIG_SCRIPT_HASH),
-        );
-    }
-    {
-        let tx = multi_sign_tx(raw_tx.clone(), &multi_sign_script, &[&keys[1], &keys[2]]);
-        let verify_result = verify(&data_loader, &tx);
         assert_error_eq!(
             verify_result.unwrap_err(),
             ScriptError::ValidationFailure(ERROR_INCORRECT_SINCE),
@@ -453,18 +446,12 @@ fn test_multisig_0_2_3_unlock_with_since() {
     }
 }
 
-fn gen_multi_sign_script(
-    keys: &[Privkey],
-    threshold: u8,
-    require_first_n: u8,
-    since: u64,
-) -> Bytes {
+fn gen_multi_sign_script(keys: &[Privkey], threshold: u8, require_first_n: u8) -> Bytes {
     let pubkeys = keys
         .iter()
         .map(|key| key.pubkey().unwrap())
         .collect::<Vec<_>>();
     let mut script = vec![0u8, require_first_n, threshold, pubkeys.len() as u8];
-    script.extend(since.to_le_bytes().into_iter());
     pubkeys.iter().for_each(|pubkey| {
         script.extend_from_slice(&pubkey.serialize());
     });