diff --git a/contracts/Proofs.sol b/contracts/Proofs.sol
index ba536b3..538e1b2 100644
--- a/contracts/Proofs.sol
+++ b/contracts/Proofs.sol
@@ -4,11 +4,17 @@ pragma solidity ^0.8.0;
 contract Proofs {
   uint256 private immutable period;
   uint256 private immutable timeout;
+  uint8 private immutable downtime;
 
-  constructor(uint256 __period, uint256 __timeout) {
+  constructor(
+    uint256 __period,
+    uint256 __timeout,
+    uint8 __downtime
+  ) {
     require(block.number > 256, "Insufficient block height");
     period = __period;
     timeout = __timeout;
+    downtime = __downtime;
   }
 
   mapping(bytes32 => bool) private ids;
@@ -95,12 +101,11 @@ contract Proofs {
       return false;
     }
     uint8 pointer = _getPointer(id, proofPeriod);
-    // TODO: make configurable:
-    if (pointer < 64) {
+    if (pointer < downtime) {
       return false;
     }
     bytes32 challenge = _getChallenge(pointer);
-    uint256 probability = (probabilities[id] * (256 - 64)) / 256;
+    uint256 probability = (probabilities[id] * (256 - downtime)) / 256;
     return uint256(challenge) % probability == 0;
   }
 
diff --git a/contracts/Storage.sol b/contracts/Storage.sol
index de2a0fd..b6806d8 100644
--- a/contracts/Storage.sol
+++ b/contracts/Storage.sol
@@ -16,10 +16,14 @@ contract Storage is Collateral, Marketplace, Proofs {
     IERC20 token,
     uint256 _proofPeriod,
     uint256 _proofTimeout,
+    uint8 _proofDowntime,
     uint256 _collateralAmount,
     uint256 _slashMisses,
     uint256 _slashPercentage
-  ) Marketplace(token, _collateralAmount) Proofs(_proofPeriod, _proofTimeout) {
+  )
+    Marketplace(token, _collateralAmount)
+    Proofs(_proofPeriod, _proofTimeout, _proofDowntime)
+  {
     collateralAmount = _collateralAmount;
     slashMisses = _slashMisses;
     slashPercentage = _slashPercentage;
diff --git a/contracts/TestProofs.sol b/contracts/TestProofs.sol
index 650004f..efc51d1 100644
--- a/contracts/TestProofs.sol
+++ b/contracts/TestProofs.sol
@@ -5,8 +5,12 @@ import "./Proofs.sol";
 
 // exposes internal functions of Proofs for testing
 contract TestProofs is Proofs {
-  constructor(uint256 __period, uint256 __timeout)
-    Proofs(__period, __timeout)
+  constructor(
+    uint256 __period,
+    uint256 __timeout,
+    uint8 __downtime
+  )
+    Proofs(__period, __timeout, __downtime)
   // solhint-disable-next-line no-empty-blocks
   {
 
diff --git a/deploy/storage.js b/deploy/storage.js
index 9633724..4bf482f 100644
--- a/deploy/storage.js
+++ b/deploy/storage.js
@@ -2,6 +2,7 @@ module.exports = async ({ deployments, getNamedAccounts }) => {
   const token = await deployments.get("TestToken")
   const proofPeriod = 10
   const proofTimeout = 5
+  const proofDowntime = 64
   const collateralAmount = 100
   const slashMisses = 3
   const slashPercentage = 10
@@ -9,6 +10,7 @@ module.exports = async ({ deployments, getNamedAccounts }) => {
     token.address,
     proofPeriod,
     proofTimeout,
+    proofDowntime,
     collateralAmount,
     slashMisses,
     slashPercentage,
diff --git a/test/Proofs.test.js b/test/Proofs.test.js
index ea8d29e..d466fa2 100644
--- a/test/Proofs.test.js
+++ b/test/Proofs.test.js
@@ -14,6 +14,7 @@ describe("Proofs", function () {
   const id = ethers.utils.randomBytes(32)
   const period = 10
   const timeout = 5
+  const downtime = 64
   const duration = 1000
   const probability = 4 // require a proof roughly once every 4 periods
 
@@ -23,7 +24,7 @@ describe("Proofs", function () {
     await snapshot()
     await ensureMinimumBlockHeight(256)
     const Proofs = await ethers.getContractFactory("TestProofs")
-    proofs = await Proofs.deploy(period, timeout)
+    proofs = await Proofs.deploy(period, timeout, downtime)
   })
 
   afterEach(async function () {