diff --git a/.github/workflows/contract.yml b/.github/workflows/contract.yml
index 1e2faa4f..cc1bf830 100644
--- a/.github/workflows/contract.yml
+++ b/.github/workflows/contract.yml
@@ -53,7 +53,7 @@ jobs:
         with:
           owner: AntelopeIO
           repo: cdt
-          target: 'v3.1.0'
+          target: 'v4.0.0'
           prereleases: false
           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 e1893d8e..73ac92a5 100644
--- a/contract/include/evm_runtime/evm_contract.hpp
+++ b/contract/include/evm_runtime/evm_contract.hpp
@@ -148,7 +148,10 @@ class [[eosio::contract]] evm_contract : public contract
 
 } // namespace evm_runtime
 
+#if __eosio_cdt_major__ <= 3
 namespace std {
+#endif
+
 template <typename DataStream>
 DataStream& operator<<(DataStream& ds, const std::basic_string<uint8_t>& bs)
 {
@@ -157,4 +160,9 @@ DataStream& operator<<(DataStream& ds, const std::basic_string<uint8_t>& bs)
       ds.write((const char*)bs.data(), bs.size());
    return ds;
 }
-} // namespace std
+
+#if __eosio_cdt_major__ <= 3
+}
+#endif
+
+