diff --git a/contracts/Marketplace.sol b/contracts/Marketplace.sol
index 1eba224..54143a9 100644
--- a/contracts/Marketplace.sol
+++ b/contracts/Marketplace.sol
@@ -3,16 +3,24 @@ pragma solidity ^0.8.0;
 
 import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
 import "./Collateral.sol";
+import "./Proofs.sol";
 
-contract Marketplace is Collateral {
+contract Marketplace is Collateral, Proofs {
   uint256 public immutable collateral;
   MarketplaceFunds private funds;
   mapping(bytes32 => Request) private requests;
   mapping(bytes32 => RequestState) private requestState;
   mapping(bytes32 => Offer) private offers;
 
-  constructor(IERC20 _token, uint256 _collateral)
+  constructor(
+    IERC20 _token,
+    uint256 _collateral,
+    uint256 _proofPeriod,
+    uint256 _proofTimeout,
+    uint8 _proofDowntime
+  )
     Collateral(_token)
+    Proofs(_proofPeriod, _proofTimeout, _proofDowntime)
     marketplaceInvariant
   {
     collateral = _collateral;
@@ -38,6 +46,26 @@ contract Marketplace is Collateral {
     emit StorageRequested(id, request.ask);
   }
 
+  function fulfillRequest(bytes32 requestId, bytes calldata proof)
+    public
+    marketplaceInvariant
+  {
+    RequestState storage state = requestState[requestId];
+    require(!state.fulfilled, "Request already fulfilled");
+
+    Request storage request = requests[requestId];
+    require(request.client != address(0), "Unknown request");
+    require(request.expiry > block.timestamp, "Request expired");
+
+    require(balanceOf(msg.sender) >= collateral, "Insufficient collateral");
+    _lock(msg.sender, requestId);
+
+    _submitProof(requestId, proof);
+
+    state.fulfilled = true;
+    emit RequestFulfilled(requestId);
+  }
+
   function offerStorage(Offer calldata offer) public marketplaceInvariant {
     require(offer.host == msg.sender, "Invalid host address");
     require(balanceOf(msg.sender) >= collateral, "Insufficient collateral");
@@ -129,6 +157,7 @@ contract Marketplace is Collateral {
   }
 
   struct RequestState {
+    bool fulfilled;
     bytes32 selectedOffer;
   }
 
@@ -140,6 +169,7 @@ contract Marketplace is Collateral {
   }
 
   event StorageRequested(bytes32 requestId, Ask ask);
+  event RequestFulfilled(bytes32 indexed requestId);
   event StorageOffered(bytes32 offerId, Offer offer, bytes32 indexed requestId);
   event OfferSelected(bytes32 offerId, bytes32 indexed requestId);
 
diff --git a/contracts/Storage.sol b/contracts/Storage.sol
index b28f69b..36cf35a 100644
--- a/contracts/Storage.sol
+++ b/contracts/Storage.sol
@@ -5,7 +5,7 @@ import "./Marketplace.sol";
 import "./Proofs.sol";
 import "./Collateral.sol";
 
-contract Storage is Collateral, Marketplace, Proofs {
+contract Storage is Collateral, Marketplace {
   uint256 public collateralAmount;
   uint256 public slashMisses;
   uint256 public slashPercentage;
@@ -21,8 +21,13 @@ contract Storage is Collateral, Marketplace, Proofs {
     uint256 _slashMisses,
     uint256 _slashPercentage
   )
-    Marketplace(token, _collateralAmount)
-    Proofs(_proofPeriod, _proofTimeout, _proofDowntime)
+    Marketplace(
+      token,
+      _collateralAmount,
+      _proofPeriod,
+      _proofTimeout,
+      _proofDowntime
+    )
   {
     collateralAmount = _collateralAmount;
     slashMisses = _slashMisses;
diff --git a/test/Marketplace.test.js b/test/Marketplace.test.js
index 598e5f4..a39e251 100644
--- a/test/Marketplace.test.js
+++ b/test/Marketplace.test.js
@@ -1,11 +1,16 @@
 const { ethers } = require("hardhat")
+const { hexlify, randomBytes } = ethers.utils
 const { expect } = require("chai")
 const { exampleRequest, exampleOffer } = require("./examples")
+const { snapshot, revert, ensureMinimumBlockHeight } = require("./evm")
 const { now, hours } = require("./time")
 const { requestId, offerId, offerToArray, askToArray } = require("./ids")
 
 describe("Marketplace", function () {
   const collateral = 100
+  const proofPeriod = 30 * 60
+  const proofTimeout = 5
+  const proofDowntime = 64
 
   let marketplace
   let token
@@ -13,6 +18,8 @@ describe("Marketplace", function () {
   let request, offer
 
   beforeEach(async function () {
+    await snapshot()
+    await ensureMinimumBlockHeight(256)
     ;[client, host1, host2, host3] = await ethers.getSigners()
     host = host1
 
@@ -23,7 +30,13 @@ describe("Marketplace", function () {
     }
 
     const Marketplace = await ethers.getContractFactory("Marketplace")
-    marketplace = await Marketplace.deploy(token.address, collateral)
+    marketplace = await Marketplace.deploy(
+      token.address,
+      collateral,
+      proofPeriod,
+      proofTimeout,
+      proofDowntime
+    )
 
     request = exampleRequest()
     request.client = client.address
@@ -33,6 +46,10 @@ describe("Marketplace", function () {
     offer.requestId = requestId(request)
   })
 
+  afterEach(async function () {
+    await revert()
+  })
+
   function switchAccount(account) {
     token = token.connect(account)
     marketplace = marketplace.connect(account)
@@ -75,6 +92,72 @@ describe("Marketplace", function () {
     })
   })
 
+  describe("fulfilling request", function () {
+    const proof = hexlify(randomBytes(42))
+
+    beforeEach(async function () {
+      switchAccount(client)
+      await token.approve(marketplace.address, request.ask.maxPrice)
+      await marketplace.requestStorage(request)
+      switchAccount(host)
+      await token.approve(marketplace.address, collateral)
+      await marketplace.deposit(collateral)
+    })
+
+    it("emits event when request is fulfilled", async function () {
+      await expect(marketplace.fulfillRequest(requestId(request), proof))
+        .to.emit(marketplace, "RequestFulfilled")
+        .withArgs(requestId(request))
+    })
+
+    it("locks collateral of host", async function () {
+      await marketplace.fulfillRequest(requestId(request), proof)
+      await expect(marketplace.withdraw()).to.be.revertedWith("Account locked")
+    })
+
+    it("is rejected when proof is incorrect", async function () {
+      let invalid = hexlify([])
+      await expect(
+        marketplace.fulfillRequest(requestId(request), invalid)
+      ).to.be.revertedWith("Invalid proof")
+    })
+
+    it("is rejected when collateral is insufficient", async function () {
+      let insufficient = collateral - 1
+      await marketplace.withdraw()
+      await token.approve(marketplace.address, insufficient)
+      await marketplace.deposit(insufficient)
+      await expect(
+        marketplace.fulfillRequest(requestId(request), proof)
+      ).to.be.revertedWith("Insufficient collateral")
+    })
+
+    it("is rejected when request already fulfilled", async function () {
+      await marketplace.fulfillRequest(requestId(request), proof)
+      await expect(
+        marketplace.fulfillRequest(requestId(request), proof)
+      ).to.be.revertedWith("Request already fulfilled")
+    })
+
+    it("is rejected when request is unknown", async function () {
+      let unknown = exampleRequest()
+      await expect(
+        marketplace.fulfillRequest(requestId(unknown), proof)
+      ).to.be.revertedWith("Unknown request")
+    })
+
+    it("is rejected when request is expired", async function () {
+      switchAccount(client)
+      let expired = { ...request, expiry: now() - hours(1) }
+      await token.approve(marketplace.address, request.ask.maxPrice)
+      await marketplace.requestStorage(expired)
+      switchAccount(host)
+      await expect(
+        marketplace.fulfillRequest(requestId(expired), proof)
+      ).to.be.revertedWith("Request expired")
+    })
+  })
+
   describe("offering storage", function () {
     beforeEach(async function () {
       switchAccount(client)