diff --git a/.github/workflows/contract.yml b/.github/workflows/contract.yml
index 1e2faa4f..b1385f83 100644
--- a/.github/workflows/contract.yml
+++ b/.github/workflows/contract.yml
@@ -53,8 +53,8 @@ jobs:
         with:
           owner: AntelopeIO
           repo: cdt
-          target: 'v3.1.0'
-          prereleases: false
+          target: 'v4.0'
+          prereleases: true
           file: 'cdt_.*amd64.deb'
           token: ${{ secrets.GITHUB_TOKEN }}
 
diff --git a/contract/include/evm_runtime/evm_contract.hpp b/contract/include/evm_runtime/evm_contract.hpp
index 5d62f83f..2a75d654 100644
--- a/contract/include/evm_runtime/evm_contract.hpp
+++ b/contract/include/evm_runtime/evm_contract.hpp
@@ -145,13 +145,3 @@ class [[eosio::contract]] evm_contract : public contract
 
 } // namespace evm_runtime
 
-namespace std {
-template <typename DataStream>
-DataStream& operator<<(DataStream& ds, const std::basic_string<uint8_t>& bs)
-{
-   ds << (unsigned_int)bs.size();
-   if (bs.size())
-      ds.write((const char*)bs.data(), bs.size());
-   return ds;
-}
-} // namespace std