diff --git a/contracts/Marketplace.sol b/contracts/Marketplace.sol
index 79adb06..5d6f9dc 100644
--- a/contracts/Marketplace.sol
+++ b/contracts/Marketplace.sol
@@ -98,6 +98,7 @@ contract Marketplace is Collateral {
     uint256 duration;
     uint256 size;
     bytes32 contentHash;
+    uint256 proofProbability;
     uint256 maxPrice;
     uint256 expiry;
     bytes32 nonce;
diff --git a/test/examples.js b/test/examples.js
index e1ed9c9..e0e3710 100644
--- a/test/examples.js
+++ b/test/examples.js
@@ -7,6 +7,7 @@ const exampleRequest = () => ({
   duration: 150, // 150 blocks ≈ half an hour
   size: 1 * 1024 * 1024 * 1024, // 1 Gigabyte
   contentHash: sha256("0xdeadbeef"),
+  proofProbability: 5, // require a proof roughly once every 5^2 periods
   maxPrice: 84,
   expiry: now() + hours(1),
   nonce: hexlify(randomBytes(32)),
diff --git a/test/ids.js b/test/ids.js
index 0f518d3..55a7ce7 100644
--- a/test/ids.js
+++ b/test/ids.js
@@ -11,6 +11,7 @@ function requestId(request) {
         "bytes32",
         "uint256",
         "uint256",
+        "uint256",
         "bytes32",
       ],
       requestToArray(request)
@@ -33,6 +34,7 @@ function requestToArray(request) {
     request.duration,
     request.size,
     request.contentHash,
+    request.proofProbability,
     request.maxPrice,
     request.expiry,
     request.nonce,