diff --git a/hyperliquid/exchange.py b/hyperliquid/exchange.py
index 688f640..91ea382 100644
--- a/hyperliquid/exchange.py
+++ b/hyperliquid/exchange.py
@@ -1078,9 +1078,11 @@ def c_validator_unregister(self) -> Any:
 
     def multi_sig(self, multi_sig_user, inner_action, signatures, nonce, vault_address=None):
         multi_sig_user = multi_sig_user.lower()
+        is_mainnet = self.base_url == MAINNET_API_URL
+        chain_id = "0xa4b1" if is_mainnet else "0x66eee"
         multi_sig_action = {
             "type": "multiSig",
-            "signatureChainId": "0x66eee",
+            "signatureChainId": chain_id,
             "signatures": signatures,
             "payload": {
                 "multiSigUser": multi_sig_user,
@@ -1088,7 +1090,6 @@ def multi_sig(self, multi_sig_user, inner_action, signatures, nonce, vault_addre
                 "action": inner_action,
             },
         }
-        is_mainnet = self.base_url == MAINNET_API_URL
         signature = sign_multi_sig_action(
             self.wallet,
             multi_sig_action,
diff --git a/hyperliquid/utils/signing.py b/hyperliquid/utils/signing.py
index 10cca4d..056202e 100644
--- a/hyperliquid/utils/signing.py
+++ b/hyperliquid/utils/signing.py
@@ -246,7 +246,8 @@ def sign_l1_action(wallet, action, active_pool, nonce, expires_after, is_mainnet
 def sign_user_signed_action(wallet, action, payload_types, primary_type, is_mainnet):
     # signatureChainId is the chain used by the wallet to sign and can be any chain.
     # hyperliquidChain determines the environment and prevents replaying an action on a different chain.
-    action["signatureChainId"] = "0x66eee"
+    if "signatureChainId" not in action:
+        action["signatureChainId"] = "0xa4b1" if is_mainnet else "0x66eee"
     action["hyperliquidChain"] = "Mainnet" if is_mainnet else "Testnet"
     data = user_signed_payload(primary_type, payload_types, action)
     return sign_inner(wallet, data)
@@ -312,9 +313,7 @@ def sign_multi_sig_l1_action_payload(
 
 
 def sign_multi_sig_action(wallet, action, is_mainnet, vault_address, nonce, expires_after):
-    action_without_tag = action.copy()
-    del action_without_tag["type"]
-    multi_sig_action_hash = action_hash(action_without_tag, vault_address, nonce, expires_after)
+    multi_sig_action_hash = action_hash(action, vault_address, nonce, expires_after)
     envelope = {
         "multiSigActionHash": multi_sig_action_hash,
         "nonce": nonce,