diff --git a/src/collator/CollatorStakingHubStorage.sol b/src/collator/CollatorStakingHubStorage.sol
index 64f598b..f9bd898 100644
--- a/src/collator/CollatorStakingHubStorage.sol
+++ b/src/collator/CollatorStakingHubStorage.sol
@@ -19,8 +19,6 @@ contract CollatorStakingHubStorage {
     address public DEPOSIT;
     // collator => stakingPool
     mapping(address => address) public poolOf;
-    // stakingPool => collator
-    mapping(address => address) public collatorOf;
     // collator => commission
     mapping(address => uint256) public commissionOf;
     // collator => user => lockTime
diff --git a/src/collator/interfaces/ICollatorStakingHub.sol b/src/collator/interfaces/ICollatorStakingHub.sol
deleted file mode 100644
index e6f8453..0000000
--- a/src/collator/interfaces/ICollatorStakingHub.sol
+++ /dev/null
@@ -1,5 +0,0 @@
-pragma solidity >=0.4.24;
-
-interface ICollatorStakingHub {
-    function exist(address c) external view returns (bool);
-}
diff --git a/src/collator/interfaces/INominationPool.sol b/src/collator/interfaces/INominationPool.sol
index 7a44190..5a11e2b 100644
--- a/src/collator/interfaces/INominationPool.sol
+++ b/src/collator/interfaces/INominationPool.sol
@@ -2,8 +2,6 @@ pragma solidity >=0.4.24;
 
 interface INominationPool {
     // Views
-    function operator() external view returns (address);
-
     function lastTimeRewardApplicable() external view returns (uint256);
 
     function rewardPerToken() external view returns (uint256);
diff --git a/src/governance/GovernanceRing.sol b/src/governance/GovernanceRing.sol
index 32b6395..ab4786a 100644
--- a/src/governance/GovernanceRing.sol
+++ b/src/governance/GovernanceRing.sol
@@ -4,7 +4,7 @@ pragma solidity 0.8.20;
 import "@openzeppelin/contracts/utils/Address.sol";
 import "@openzeppelin/contracts/utils/structs/EnumerableSet.sol";
 import "@openzeppelin/contracts-upgradeable/token/ERC20/ERC20Upgradeable.sol";
-import "@openzeppelin/contracts-upgradeable/access/AccessControlUpgradeable.sol";
+import "@openzeppelin/contracts-upgradeable/access/extensions/AccessControlEnumerableUpgradeable.sol";
 import "@openzeppelin/contracts-upgradeable/token/ERC20/extensions/ERC20PermitUpgradeable.sol";
 import "@openzeppelin/contracts-upgradeable/token/ERC20/extensions/ERC20VotesUpgradeable.sol";
 import "@openzeppelin/contracts-upgradeable/utils/ReentrancyGuardUpgradeable.sol";
@@ -15,7 +15,7 @@ import "../deposit/interfaces/IDeposit.sol";
 contract GovernanceRing is
     Initializable,
     ERC20Upgradeable,
-    AccessControlUpgradeable,
+    AccessControlEnumerableUpgradeable,
     ERC20PermitUpgradeable,
     ERC20VotesUpgradeable,
     ReentrancyGuardUpgradeable
@@ -43,7 +43,7 @@ contract GovernanceRing is
     function initialize(address admin, address dps, string memory name, string memory symbol) public initializer {
         DEPOSIT = IDeposit(dps);
         __ERC20_init(name, symbol);
-        __AccessControl_init();
+        __AccessControlEnumerable_init();
         __ERC20Permit_init(symbol);
         __ERC20Votes_init();
         __ReentrancyGuard_init();