diff --git a/app/sql.js b/app/sql.js
index 95aa17e82..b64c4feac 100644
--- a/app/sql.js
+++ b/app/sql.js
@@ -1534,22 +1534,18 @@ async function saveMessage(data, { forceSave } = {}) {
   return toCreate.id;
 }
 
-async function saveSeenMessageHashes(incomingHashes) {
+async function saveSeenMessageHashes(arrayOfHashes) {
   let promise;
-  const hashList = incomingHashes.map(h => h.hash);
-  const dupHashes = await getSeenMessagesByHashList(hashList);
-  const newHashes = incomingHashes.filter(h => !dupHashes.includes(h.hash));
 
   db.serialize(() => {
     promise = Promise.all([
       db.run('BEGIN TRANSACTION;'),
-      ...map(newHashes, hashData => saveSeenMessageHash(hashData)),
+      ...map(arrayOfHashes, hashData => saveSeenMessageHash(hashData)),
       db.run('COMMIT TRANSACTION;'),
     ]);
   });
 
   await promise;
-  return newHashes;
 }
 
 async function saveSeenMessageHash(data) {
diff --git a/background.html b/background.html
index f2a11cda3..7fa85684e 100644
--- a/background.html
+++ b/background.html
@@ -723,6 +723,7 @@
   <script type='text/javascript' src='js/models/blockedNumbers.js'></script>
   <script type='text/javascript' src='js/models/profile.js'></script>
   <script type='text/javascript' src='js/expiring_messages.js'></script>
+  <script type='text/javascript' src='js/queue_manager.js'></script>
 
   <script type='text/javascript' src='js/chromium.js'></script>
   <script type='text/javascript' src='js/registration.js'></script>
diff --git a/js/modules/data.js b/js/modules/data.js
index 622750aff..e850c723d 100644
--- a/js/modules/data.js
+++ b/js/modules/data.js
@@ -788,7 +788,7 @@ async function cleanSeenMessages() {
 }
 
 async function saveSeenMessageHashes(data) {
-  return channels.saveSeenMessageHashes(_cleanData(data));
+  await channels.saveSeenMessageHashes(_cleanData(data));
 }
 
 async function saveSeenMessageHash(data) {
diff --git a/js/queue_manager.js b/js/queue_manager.js
new file mode 100644
index 000000000..7202c83dc
--- /dev/null
+++ b/js/queue_manager.js
@@ -0,0 +1,28 @@
+/* eslint-disable more/no-then */
+
+// eslint-disable-next-line func-names
+(function() {
+  'use strict'
+
+  class JobQueue {
+    constructor() {
+      this.pending = Promise.resolve();
+    }
+
+    add(job) {
+      const previous = this.pending || Promise.resolve();
+      this.pending = previous.then(job, job);
+      const current = this.pending;
+
+      current.then(() => {
+        if (this.pending === current) {
+          delete this.pending;
+        }
+      });
+
+      return current;
+    }
+  }
+
+  window.JobQueue = JobQueue;
+})();
diff --git a/libtextsecure/http-resources.js b/libtextsecure/http-resources.js
index 995655181..4ac3ee38c 100644
--- a/libtextsecure/http-resources.js
+++ b/libtextsecure/http-resources.js
@@ -45,15 +45,16 @@
   const filterIncomingMessages = async function filterIncomingMessages(
     messages
   ) {
-    const incomingHashes = messages.map(m => ({
+    const incomingHashes = messages.map(m => m.hash);
+    const dupHashes = await window.Signal.Data.getSeenMessagesByHashList(
+      incomingHashes
+    );
+    const newMessages = messages.filter(m => !dupHashes.includes(m.hash));
+    const newHashes = newMessages.map(m => ({
       expiresAt: m.expiration,
       hash: m.hash,
     }));
-    let newHashes = await window.Signal.Data.saveSeenMessageHashes(
-      incomingHashes
-    );
-    newHashes = newHashes.map(h => h.hash);
-    const newMessages = messages.filter(m => newHashes.includes(m.hash));
+    await window.Signal.Data.saveSeenMessageHashes(newHashes);
     return newMessages;
   };
 
@@ -64,9 +65,12 @@
       handleRequest = request => request.respond(404, 'Not found');
     }
     let connected = false;
+    const jobQueue = new window.JobQueue();
 
     const processMessages = async messages => {
-      const newMessages = await filterIncomingMessages(messages);
+      const newMessages = await jobQueue.add(
+        () => filterIncomingMessages(messages)
+      );
       newMessages.forEach(async message => {
         const { data } = message;
         this.handleMessage(data);