diff --git a/contracts/apps/disputable/IAgreement.sol b/contracts/apps/disputable/IAgreement.sol
index 105f35958..40a5de41d 100644
--- a/contracts/apps/disputable/IAgreement.sol
+++ b/contracts/apps/disputable/IAgreement.sol
@@ -99,12 +99,18 @@ contract IAgreement is IArbitrable, IACLOracle {
             uint64 endDate,
             bytes context,
             uint256 settlementOffer,
-            uint256 arbitratorFeeAmount,
-            ERC20 arbitratorFeeToken,
             ChallengeState state,
             bool submitterFinishedEvidence,
             bool challengerFinishedEvidence,
             uint256 disputeId,
             uint256 ruling
         );
+
+    function getChallengeArbitratorFees(uint256 _challengeId) external view
+        returns (
+            uint256 challengerArbitratorFeesAmount,
+            ERC20 challengerArbitratorFeesToken,
+            uint256 submitterArbitratorFeesAmount,
+            ERC20 submitterArbitratorFeesToken
+        );
 }
diff --git a/contracts/test/mocks/apps/disputable/AgreementMock.sol b/contracts/test/mocks/apps/disputable/AgreementMock.sol
index 2796c84c4..7f89ff286 100644
--- a/contracts/test/mocks/apps/disputable/AgreementMock.sol
+++ b/contracts/test/mocks/apps/disputable/AgreementMock.sol
@@ -101,8 +101,6 @@ contract AgreementMock is IAgreement {
             uint64,
             bytes,
             uint256,
-            uint256,
-            ERC20,
             ChallengeState,
             bool,
             bool,
@@ -113,15 +111,26 @@ contract AgreementMock is IAgreement {
         // do nothing
     }
 
-    function submitEvidence(uint256 _disputeId, bytes _evidence, bool _finished) external {
+    function getChallengeArbitratorFees(uint256) external view
+        returns (
+            uint256,
+            ERC20,
+            uint256,
+            ERC20
+        )
+    {
+        // do nothing
+    }
+
+    function submitEvidence(uint256, bytes, bool) external {
         // do nothing
     }
 
-    function rule(uint256 _disputeId, uint256 _ruling) external {
+    function rule(uint256, uint256) external {
         // do nothing
     }
 
-    function supportsInterface(bytes4 _interfaceId) public pure returns (bool) {
+    function supportsInterface(bytes4) public pure returns (bool) {
         // do nothing
     }
 
diff --git a/package.json b/package.json
index 0f14f549f..e0500616a 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@aragon/os",
-  "version": "5.0.0-beta.5",
+  "version": "5.0.0-beta.6",
   "author": "Aragon Association <legal@aragon.org>",
   "license": "(GPL-3.0-or-later OR MIT)",
   "repository": "https://github.com/aragon/aragonOS",