diff --git a/lib/hk-util.js b/lib/hk-util.js
index 513fac04f..0fafcdb91 100644
--- a/lib/hk-util.js
+++ b/lib/hk-util.js
@@ -445,48 +445,6 @@ const getHistoryAsync = (Env, channelName, lastKnownHash, beforeHash, handler, c
     });
 };
 
-/*  getOlderHistory
-    * allows clients to query for all messages until a known hash is read
-    * stores all messages in history as they are read
-      * can therefore be very expensive for memory
-      * should probably be converted to a streaming interface
-
-    Used by:
-    * GET_HISTORY_RANGE
-*/
-const getOlderHistory = function (Env, channelName, oldestKnownHash, cb) { // XXX child process
-    const store = Env.store;
-    const Log = Env.Log;
-    var messageBuffer = [];
-    var found = false;
-    store.getMessages(channelName, function (msgStr) {
-        if (found) { return; }
-
-        let parsed = tryParse(Env, msgStr);
-        if (typeof parsed === "undefined") { return; }
-
-        // identify classic metadata messages by their inclusion of a channel.
-        // and don't send metadata, since:
-        // 1. the user won't be interested in it
-        // 2. this metadata is potentially incomplete/incorrect
-        if (isMetadataMessage(parsed)) { return; }
-
-        var content = parsed[4];
-        if (typeof(content) !== 'string') { return; }
-
-        var hash = getHash(content, Log);
-        if (hash === oldestKnownHash) {
-            found = true;
-        }
-        messageBuffer.push(parsed);
-    }, function (err) {
-        if (err && err.code !== 'ENOENT') {
-            Log.error("HK_GET_OLDER_HISTORY", err);
-        }
-        cb(messageBuffer);
-    });
-};
-
 const handleRPC = function (Env, Server, seq, userId, parsed) {
     const HISTORY_KEEPER_ID = Env.id;
 
@@ -662,7 +620,11 @@ const handleGetHistoryRange = function (Env, Server, seq, userId, parsed) {
     }
 
     Server.send(userId, [seq, 'ACK']);
-    return void getOlderHistory(Env, channelName, oldestKnownHash, function (messages) {
+    Env.getOlderHistory(channelName, oldestKnownHash, function (err, messages) {
+        if (err && err.code !== 'ENOENT') {
+            Env.Log.error("HK_GET_OLDER_HISTORY", err);
+        }
+
         var toSend = [];
         if (typeof (desiredMessages) === "number") {
             toSend = messages.slice(-desiredMessages);
@@ -914,8 +876,18 @@ HK.initializeIndexWorkers = function (Env, config, _cb) {
             });
         };
 
+        Env.getOlderHistory = function (channel, oldestKnownHash, cb) {
+            Env.store.getWeakLock(channel, function (next) {
+                sendCommand({
+                    channel: channel,
+                    command: "GET_OLDER_HISTORY",
+                    hash: oldestKnownHash,
+                }, Util.both(next, cb));
+            });
+        };
+
         //console.log("index workers ready");
-        cb(void 0, sendCommand);
+        cb(void 0);
     });
 };
 
diff --git a/lib/workers/compute-index.js b/lib/workers/compute-index.js
index 17a292059..e46e40bcc 100644
--- a/lib/workers/compute-index.js
+++ b/lib/workers/compute-index.js
@@ -144,9 +144,53 @@ const computeMetadata = function (data, cb, errorHandler) {
     });
 };
 
+/*  getOlderHistory
+    * allows clients to query for all messages until a known hash is read
+    * stores all messages in history as they are read
+      * can therefore be very expensive for memory
+      * should probably be converted to a streaming interface
+
+    Used by:
+    * GET_HISTORY_RANGE
+*/
+
+const getOlderHistory = function (data, cb) {
+    const oldestKnownHash = data.hash;
+    const channelName = data.channel;
+
+    //const store = Env.store;
+    //const Log = Env.Log;
+    var messageBuffer = [];
+    var found = false;
+    store.getMessages(channelName, function (msgStr) {
+        if (found) { return; }
+
+        let parsed = tryParse(Env, msgStr);
+        if (typeof parsed === "undefined") { return; }
+
+        // identify classic metadata messages by their inclusion of a channel.
+        // and don't send metadata, since:
+        // 1. the user won't be interested in it
+        // 2. this metadata is potentially incomplete/incorrect
+        if (HK.isMetadataMessage(parsed)) { return; }
+
+        var content = parsed[4];
+        if (typeof(content) !== 'string') { return; }
+
+        var hash = HK.getHash(content);
+        if (hash === oldestKnownHash) {
+            found = true;
+        }
+        messageBuffer.push(parsed);
+    }, function (err) {
+        cb(err, messageBuffer);
+    });
+};
+
 const COMMANDS = {
     COMPUTE_INDEX: computeIndex,
     COMPUTE_METADATA: computeMetadata,
+    GET_OLDER_HISTORY: getOlderHistory,
 };
 
 process.on('message', function (data) {