diff --git a/ethereum/eth/src/main/java/tech/pegasys/pantheon/ethereum/eth/manager/task/GetNodeDataFromPeerTask.java b/ethereum/eth/src/main/java/tech/pegasys/pantheon/ethereum/eth/manager/task/GetNodeDataFromPeerTask.java
index c9582af02e..25f507afb7 100644
--- a/ethereum/eth/src/main/java/tech/pegasys/pantheon/ethereum/eth/manager/task/GetNodeDataFromPeerTask.java
+++ b/ethereum/eth/src/main/java/tech/pegasys/pantheon/ethereum/eth/manager/task/GetNodeDataFromPeerTask.java
@@ -12,7 +12,7 @@
  */
 package tech.pegasys.pantheon.ethereum.eth.manager.task;
 
-import static java.util.Collections.emptyList;
+import static java.util.Collections.emptyMap;
 
 import tech.pegasys.pantheon.ethereum.core.Hash;
 import tech.pegasys.pantheon.ethereum.eth.manager.EthContext;
@@ -27,15 +27,17 @@
 import tech.pegasys.pantheon.util.bytes.BytesValue;
 
 import java.util.Collection;
+import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
+import java.util.Map;
 import java.util.Optional;
 import java.util.Set;
 
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 
-public class GetNodeDataFromPeerTask extends AbstractPeerRequestTask<List<BytesValue>> {
+public class GetNodeDataFromPeerTask extends AbstractPeerRequestTask<Map<Hash, BytesValue>> {
 
   private static final Logger LOG = LogManager.getLogger();
 
@@ -63,26 +65,31 @@ protected ResponseStream sendRequest(final EthPeer peer) throws PeerNotConnected
   }
 
   @Override
-  protected Optional<List<BytesValue>> processResponse(
+  protected Optional<Map<Hash, BytesValue>> processResponse(
       final boolean streamClosed, final MessageData message, final EthPeer peer) {
     if (streamClosed) {
       // We don't record this as a useless response because it's impossible to know if a peer has
       // the data we're requesting.
-      return Optional.of(emptyList());
+      return Optional.of(emptyMap());
     }
     final NodeDataMessage nodeDataMessage = NodeDataMessage.readFrom(message);
     final List<BytesValue> nodeData = nodeDataMessage.nodeData();
-    if (nodeData.isEmpty()) {
-      return Optional.empty();
-    } else if (nodeData.size() > hashes.size()) {
+    if (nodeData.size() > hashes.size()) {
       // Can't be the response to our request
       return Optional.empty();
     }
+    return mapNodeDataByHash(nodeData);
+  }
 
-    if (nodeData.stream().anyMatch(data -> !hashes.contains(Hash.hash(data)))) {
-      // Message contains unrequested data, must not be the response to our request.
-      return Optional.empty();
+  private Optional<Map<Hash, BytesValue>> mapNodeDataByHash(final List<BytesValue> nodeData) {
+    final Map<Hash, BytesValue> nodeDataByHash = new HashMap<>();
+    for (BytesValue data : nodeData) {
+      final Hash hash = Hash.hash(data);
+      if (!hashes.contains(hash)) {
+        return Optional.empty();
+      }
+      nodeDataByHash.put(hash, data);
     }
-    return Optional.of(nodeData);
+    return Optional.of(nodeDataByHash);
   }
 }
diff --git a/ethereum/eth/src/main/java/tech/pegasys/pantheon/ethereum/eth/sync/worldstate/WorldStateDownloader.java b/ethereum/eth/src/main/java/tech/pegasys/pantheon/ethereum/eth/sync/worldstate/WorldStateDownloader.java
index e7786c3140..a60778c4a4 100644
--- a/ethereum/eth/src/main/java/tech/pegasys/pantheon/ethereum/eth/sync/worldstate/WorldStateDownloader.java
+++ b/ethereum/eth/src/main/java/tech/pegasys/pantheon/ethereum/eth/sync/worldstate/WorldStateDownloader.java
@@ -37,7 +37,6 @@
 import java.time.Duration;
 import java.util.ArrayList;
 import java.util.Collections;
-import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
@@ -240,7 +239,7 @@ private CompletableFuture<?> waitForNewPeer() {
         .timeout(WaitForPeerTask.create(ethContext, ethTasksTimer), Duration.ofSeconds(5));
   }
 
-  private CompletableFuture<AbstractPeerTask<List<BytesValue>>> sendAndProcessRequests(
+  private CompletableFuture<AbstractPeerTask<Map<Hash, BytesValue>>> sendAndProcessRequests(
       final EthPeer peer,
       final List<Task<NodeDataRequest>> requestTasks,
       final BlockHeader blockHeader) {
@@ -250,13 +249,12 @@ private CompletableFuture<AbstractPeerTask<List<BytesValue>>> sendAndProcessRequ
             .map(NodeDataRequest::getHash)
             .distinct()
             .collect(Collectors.toList());
-    final AbstractPeerTask<List<BytesValue>> ethTask =
+    final AbstractPeerTask<Map<Hash, BytesValue>> ethTask =
         GetNodeDataFromPeerTask.forHashes(ethContext, hashes, ethTasksTimer).assignPeer(peer);
     outstandingRequests.add(ethTask);
     return ethTask
         .run()
         .thenApply(PeerTaskResult::getResult)
-        .thenApply(this::mapNodeDataByHash)
         .exceptionally(
             error -> {
               final Throwable rootCause = ExceptionUtils.rootCause(error);
@@ -276,10 +274,10 @@ private CompletableFuture<AbstractPeerTask<List<BytesValue>>> sendAndProcessRequ
                         () -> storeData(requestTasks, blockHeader, ethTask, data)));
   }
 
-  private CompletableFuture<AbstractPeerTask<List<BytesValue>>> storeData(
+  private CompletableFuture<AbstractPeerTask<Map<Hash, BytesValue>>> storeData(
       final List<Task<NodeDataRequest>> requestTasks,
       final BlockHeader blockHeader,
-      final AbstractPeerTask<List<BytesValue>> ethTask,
+      final AbstractPeerTask<Map<Hash, BytesValue>> ethTask,
       final Map<Hash, BytesValue> data) {
     final Updater storageUpdater = worldStateStorage.updater();
     for (final Task<NodeDataRequest> task : requestTasks) {
@@ -378,11 +376,4 @@ private synchronized void markDone() {
   private boolean isRootState(final BlockHeader blockHeader, final NodeDataRequest request) {
     return request.getHash().equals(blockHeader.getStateRoot());
   }
-
-  private Map<Hash, BytesValue> mapNodeDataByHash(final List<BytesValue> data) {
-    // Map data by hash
-    final Map<Hash, BytesValue> dataByHash = new HashMap<>();
-    data.forEach(d -> dataByHash.put(Hash.hash(d), d));
-    return dataByHash;
-  }
 }
diff --git a/ethereum/eth/src/test/java/tech/pegasys/pantheon/ethereum/eth/manager/task/GetNodeDataFromPeerTaskTest.java b/ethereum/eth/src/test/java/tech/pegasys/pantheon/ethereum/eth/manager/task/GetNodeDataFromPeerTaskTest.java
index c22988d8a6..f0b0e23128 100644
--- a/ethereum/eth/src/test/java/tech/pegasys/pantheon/ethereum/eth/manager/task/GetNodeDataFromPeerTaskTest.java
+++ b/ethereum/eth/src/test/java/tech/pegasys/pantheon/ethereum/eth/manager/task/GetNodeDataFromPeerTaskTest.java
@@ -12,7 +12,6 @@
  */
 package tech.pegasys.pantheon.ethereum.eth.manager.task;
 
-import static java.util.stream.Collectors.toList;
 import static org.assertj.core.api.Assertions.assertThat;
 
 import tech.pegasys.pantheon.ethereum.core.BlockHeader;
@@ -22,43 +21,52 @@
 import tech.pegasys.pantheon.ethereum.eth.manager.task.AbstractPeerTask.PeerTaskResult;
 import tech.pegasys.pantheon.util.bytes.BytesValue;
 
-import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 
-public class GetNodeDataFromPeerTaskTest extends PeerMessageTaskTest<List<BytesValue>> {
+import com.google.common.collect.Lists;
+
+public class GetNodeDataFromPeerTaskTest extends PeerMessageTaskTest<Map<Hash, BytesValue>> {
 
   @Override
-  protected List<BytesValue> generateDataToBeRequested() {
-    final List<BytesValue> requestedData = new ArrayList<>();
+  protected Map<Hash, BytesValue> generateDataToBeRequested() {
+    final Map<Hash, BytesValue> requestedData = new HashMap<>();
     for (int i = 0; i < 3; i++) {
       final BlockHeader blockHeader = blockchain.getBlockHeader(10 + i).get();
-      requestedData.add(
+      requestedData.put(
+          Hash.hash(
+              protocolContext.getWorldStateArchive().getNodeData(blockHeader.getStateRoot()).get()),
           protocolContext.getWorldStateArchive().getNodeData(blockHeader.getStateRoot()).get());
     }
     return requestedData;
   }
 
   @Override
-  protected EthTask<PeerTaskResult<List<BytesValue>>> createTask(
-      final List<BytesValue> requestedData) {
-    final List<Hash> hashes = requestedData.stream().map(Hash::hash).collect(toList());
+  protected EthTask<PeerTaskResult<Map<Hash, BytesValue>>> createTask(
+      final Map<Hash, BytesValue> requestedData) {
+    final List<Hash> hashes = Lists.newArrayList(requestedData.keySet());
     return GetNodeDataFromPeerTask.forHashes(ethContext, hashes, ethTasksTimer);
   }
 
   @Override
   protected void assertPartialResultMatchesExpectation(
-      final List<BytesValue> requestedData, final List<BytesValue> partialResponse) {
+      final Map<Hash, BytesValue> requestedData, final Map<Hash, BytesValue> partialResponse) {
     assertThat(partialResponse.size()).isLessThanOrEqualTo(requestedData.size());
     assertThat(partialResponse.size()).isGreaterThan(0);
-    assertThat(requestedData).containsAll(partialResponse);
+    for (Map.Entry<Hash, BytesValue> data : partialResponse.entrySet()) {
+      assertThat(requestedData.get(data.getKey())).isEqualTo(data.getValue());
+    }
   }
 
   @Override
   protected void assertResultMatchesExpectation(
-      final List<BytesValue> requestedData,
-      final PeerTaskResult<List<BytesValue>> response,
+      final Map<Hash, BytesValue> requestedData,
+      final PeerTaskResult<Map<Hash, BytesValue>> response,
       final EthPeer respondingPeer) {
-    assertThat(response.getResult()).containsExactlyInAnyOrderElementsOf(requestedData);
-    assertThat(response.getPeer()).isEqualTo(respondingPeer);
+    assertThat(response.getResult().size()).isEqualTo(requestedData.size());
+    for (Map.Entry<Hash, BytesValue> data : response.getResult().entrySet()) {
+      assertThat(requestedData.get(data.getKey())).isEqualTo(data.getValue());
+    }
   }
 }