diff --git a/.github/workflows/checks.yaml b/.github/workflows/checks.yaml
index ebccd602..8567580a 100644
--- a/.github/workflows/checks.yaml
+++ b/.github/workflows/checks.yaml
@@ -19,7 +19,7 @@ jobs:
       - name: Install Rust
         uses: actions-rust-lang/setup-rust-toolchain@v1
         with:
-          toolchain: nightly-2023-08-21
+          toolchain: nightly-2024-01-01
           components: rustfmt, clippy
 
       - uses: actions/setup-node@v3
@@ -44,7 +44,7 @@ jobs:
       - name: Install Rust
         uses: actions-rust-lang/setup-rust-toolchain@v1
         with:
-          toolchain: nightly-2023-08-21
+          toolchain: nightly-2024-01-01
 
       - name: Build Code
         run: make all
diff --git a/.github/workflows/docs.yaml b/.github/workflows/docs.yaml
index 4e8ceeba..870161b1 100644
--- a/.github/workflows/docs.yaml
+++ b/.github/workflows/docs.yaml
@@ -33,7 +33,7 @@ jobs:
       - name: Install Rust
         uses: actions-rust-lang/setup-rust-toolchain@v1
         with:
-          toolchain: nightly-2023-08-21
+          toolchain: nightly-2024-01-01
       - name: Setup Pages
         uses: actions/configure-pages@v3
 
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 7e50ae41..4f23d664 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -48,7 +48,7 @@ jobs:
       - name: Install Rust
         uses: actions-rust-lang/setup-rust-toolchain@v1
         with:
-          toolchain: nightly-2023-08-21
+          toolchain: nightly-2024-01-01
       - name: Install target
         run: rustup target add ${{ matrix.arch }}
 
diff --git a/.github/workflows/tests.yaml b/.github/workflows/tests.yaml
index 973f28b1..4fa5eb8b 100644
--- a/.github/workflows/tests.yaml
+++ b/.github/workflows/tests.yaml
@@ -24,7 +24,7 @@ jobs:
     - name: Install Rust
       uses: actions-rust-lang/setup-rust-toolchain@v1
       with:
-        toolchain: nightly-2023-08-21
+        toolchain: nightly-2024-01-01
 
     - name: Install cargo-nextest
       run: cargo install cargo-nextest
diff --git a/SUPPORTED_APIS.md b/SUPPORTED_APIS.md
index e560c0fb..f0ffe7b8 100644
--- a/SUPPORTED_APIS.md
+++ b/SUPPORTED_APIS.md
@@ -129,7 +129,7 @@ The `status` options are:
 | [`ZKS`](#zks-namespace) | [`zks_getTokenPrice`](#zks_getTokenPrice) | `SUPPORTED` | Gets the USD price of a token <br />_(`ETH` is hard-coded to `1_500`, while some others are `1`)_ |
 | [`ZKS`](#zks-namespace) | [`zks_getTransactionDetails`](#zks_gettransactiondetails) | `SUPPORTED` | Returns data from a specific transaction given by the transaction hash |
 | `ZKS` | `zks_L1BatchNumber` | `NOT IMPLEMENTED` | Returns the latest L1 batch number |
-| `ZKS` | `zks_L1ChainId` | `NOT IMPLEMENTED` | Returns the chain id of the underlying L1 |
+| [`ZKS`](#zks-namespace) | [`zks_L1ChainId`](#zks_l1chainid) | `IMPLEMENTED` | Returns the chain id of the underlying L1 |
 
 ## `CONFIG NAMESPACE`
 
@@ -1979,3 +1979,26 @@ curl --request POST \
     "params": ["0x364d6D0333432C3Ac016Ca832fb8594A8cE43Ca6"]
 }'
 ```
+
+### `zks_L1ChainId`
+
+[source](src/node/zks.rs)
+
+Returns the chain id of the underlying L1.
+
+#### Arguments
+
++ _NONE_
+
+#### Status
+
+`SUPPORTED`
+
+#### Example
+
+```bash
+curl --request POST \
+  --url http://localhost:8011/ \
+  --header 'content-type: application/json' \
+  --data '{"jsonrpc": "2.0","id": "1","method": "zks_L1ChainId","params": []}'
+```
diff --git a/etc/system-contracts/bootloader/test_infra/rust-toolchain b/etc/system-contracts/bootloader/test_infra/rust-toolchain
index 9a87fb21..5951a259 100644
--- a/etc/system-contracts/bootloader/test_infra/rust-toolchain
+++ b/etc/system-contracts/bootloader/test_infra/rust-toolchain
@@ -1 +1 @@
-nightly-2023-08-21
+nightly-2024-01-01
diff --git a/rust-toolchain.toml b/rust-toolchain.toml
index 14381872..d07be424 100644
--- a/rust-toolchain.toml
+++ b/rust-toolchain.toml
@@ -1,3 +1,3 @@
 [toolchain]
-channel = "nightly-2023-08-21"
+channel = "nightly-2024-01-01"
 components = ["rustfmt", "clippy"]
\ No newline at end of file
diff --git a/src/main.rs b/src/main.rs
index 8637bbd0..46aae730 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -372,7 +372,7 @@ async fn main() -> anyhow::Result<()> {
     tracing::info!("");
     tracing::info!("Rich Accounts");
     tracing::info!("=============");
-    for (_, wallet) in LEGACY_RICH_WALLETS.iter().enumerate() {
+    for wallet in LEGACY_RICH_WALLETS.iter() {
         let address = wallet.0;
         node.set_rich_account(H160::from_str(address).unwrap());
     }
diff --git a/src/node/zks.rs b/src/node/zks.rs
index 7b83b540..4b26ab6d 100644
--- a/src/node/zks.rs
+++ b/src/node/zks.rs
@@ -176,7 +176,8 @@ impl<S: ForkSource + std::fmt::Debug + Clone + Send + Sync + 'static> ZksNamespa
     }
 
     fn l1_chain_id(&self) -> RpcResult<zksync_basic_types::U64> {
-        not_implemented("zks_L1ChainId")
+        use crate::namespaces::EthNamespaceT;
+        self.chain_id()
     }
 
     fn get_confirmed_tokens(
@@ -515,6 +516,7 @@ mod tests {
 
     use crate::cache::CacheConfig;
     use crate::fork::ForkDetails;
+    use crate::node::TEST_NODE_NETWORK_ID;
     use crate::testing;
     use crate::testing::{ForkBlockConfig, MockServer};
     use crate::{http_fork_source::HttpForkSource, node::InMemoryNode};
@@ -1043,6 +1045,13 @@ mod tests {
         assert_eq!(&balances[0].name, "Ether");
     }
 
+    #[tokio::test]
+    async fn test_get_l1_chain_id() {
+        let node = InMemoryNode::<HttpForkSource>::default();
+        let chain_id = node.l1_chain_id().await.expect("get chain id").as_u32();
+        assert_eq!(TEST_NODE_NETWORK_ID, chain_id);
+    }
+
     #[tokio::test]
     async fn test_get_all_account_balances_forked() {
         let cbeth_address = Address::from_str("0x75af292c1c9a37b3ea2e6041168b4e48875b9ed5")
diff --git a/test_endpoints.http b/test_endpoints.http
index 5a2d56ff..91ac0cad 100644
--- a/test_endpoints.http
+++ b/test_endpoints.http
@@ -751,6 +751,17 @@ content-type: application/json
 POST http://localhost:8011
 content-type: application/json
 
+{
+    "jsonrpc": "2.0",
+    "id": "1",
+    "method": "zks_L1ChainId",
+    "params": []
+}
+
+###
+POST http://localhost:8011
+content-type: application/json
+
 {
     "jsonrpc": "2.0",
     "id": "1",