diff --git a/contracts/src/CollateralRegistry.sol b/contracts/src/CollateralRegistry.sol
index 73590e0c1..af602db9c 100644
--- a/contracts/src/CollateralRegistry.sol
+++ b/contracts/src/CollateralRegistry.sol
@@ -195,7 +195,7 @@ contract CollateralRegistry is LiquityBase, ICollateralRegistry {
     }
 
     // Updates the `baseRate` state with math from `_getUpdatedBaseRateFromRedemption`
-    function _updateBaseRateAndGetRedemptionRate(IBoldToken _boldToken, uint256 _boldAmount, uint256 _totalBoldSupplyAtStart)
+    function _updateBaseRateAndGetRedemptionRate(uint256 _boldAmount, uint256 _totalBoldSupplyAtStart)
         internal
     {
         uint256 newBaseRate = _getUpdatedBaseRateFromRedemption(_boldAmount, _totalBoldSupplyAtStart);