diff --git a/libloki/api.js b/libloki/api.js
index ef1baccf4..b18746ef8 100644
--- a/libloki/api.js
+++ b/libloki/api.js
@@ -193,6 +193,29 @@
     });
     return syncMessage;
   }
+  function createOpenGroupsSyncProtoMessage(conversations) {
+    // We only want to sync across open groups that we haven't left
+    const sessionOpenGroups = conversations.filter(
+      c => c.isPublic() && !c.isRss() && !c.get('left')
+    );
+
+    if (sessionOpenGroups.length === 0) {
+      return null;
+    }
+
+    const openGroups = sessionOpenGroups.map(
+      conversation =>
+        new textsecure.protobuf.SyncMessage.OpenGroupDetails({
+          url: conversation.id.split('@').pop(),
+          channelId: conversation.get('channelId'),
+        })
+    );
+
+    const syncMessage = new textsecure.protobuf.SyncMessage({
+      openGroups,
+    });
+    return syncMessage;
+  }
   async function sendPairingAuthorisation(authorisation, recipientPubKey) {
     const pairingAuthorisation = createPairingAuthorisationProtoMessage(
       authorisation
@@ -257,5 +280,6 @@
     sendUnpairingMessageToSecondary,
     createContactSyncProtoMessage,
     createGroupSyncProtoMessage,
+    createOpenGroupsSyncProtoMessage,
   };
 })();
diff --git a/libtextsecure/account_manager.js b/libtextsecure/account_manager.js
index 088422630..b26ceda99 100644
--- a/libtextsecure/account_manager.js
+++ b/libtextsecure/account_manager.js
@@ -638,6 +638,7 @@
       const conversations = window.getConversations().models;
       textsecure.messaging.sendContactSyncMessage(conversations);
       textsecure.messaging.sendGroupSyncMessage(conversations);
+      textsecure.messaging.sendOpenGroupsSyncMessage(conversations);
     },
     validatePubKeyHex(pubKey) {
       const c = new Whisper.Conversation({
diff --git a/libtextsecure/message_receiver.js b/libtextsecure/message_receiver.js
index 81adb351f..8397df5f8 100644
--- a/libtextsecure/message_receiver.js
+++ b/libtextsecure/message_receiver.js
@@ -1505,6 +1505,8 @@ MessageReceiver.prototype.extend({
       return this.handleContacts(envelope, syncMessage.contacts);
     } else if (syncMessage.groups) {
       return this.handleGroups(envelope, syncMessage.groups);
+    } else if (syncMessage.openGroups) {
+      return this.handleOpenGroups(envelope, syncMessage.openGroups);
     } else if (syncMessage.blocked) {
       return this.handleBlocked(envelope, syncMessage.blocked);
     } else if (syncMessage.request) {
@@ -1606,6 +1608,12 @@ MessageReceiver.prototype.extend({
       });
     });
   },
+  handleOpenGroups(envelope, openGroups) {
+    openGroups.forEach(({ url, channelId }) => {
+      window.attemptConnection(url, channelId);
+    });
+    return this.removeFromCache(envelope);
+  },
   handleBlocked(envelope, blocked) {
     window.log.info('Setting these numbers as blocked:', blocked.numbers);
     textsecure.storage.put('blocked', blocked.numbers);
diff --git a/libtextsecure/sendmessage.js b/libtextsecure/sendmessage.js
index 3d39d472d..8775c9987 100644
--- a/libtextsecure/sendmessage.js
+++ b/libtextsecure/sendmessage.js
@@ -727,6 +727,38 @@ MessageSender.prototype = {
     return Promise.all(syncPromises);
   },
 
+  sendOpenGroupsSyncMessage(conversations) {
+    // If we havn't got a primaryDeviceKey then we are in the middle of pairing
+    // primaryDevicePubKey is set to our own number if we are the master device
+    const primaryDeviceKey = window.storage.get('primaryDevicePubKey');
+    if (!primaryDeviceKey) {
+      return Promise.resolve();
+    }
+
+    // Send the whole list of open groups in a single message
+
+    const openGroupsSyncMessage = libloki.api.createOpenGroupsSyncProtoMessage(
+      conversations
+    );
+
+    if (!openGroupsSyncMessage) {
+      window.log.info('No open groups to sync');
+      return Promise.resolve();
+    }
+
+    const contentMessage = new textsecure.protobuf.Content();
+    contentMessage.syncMessage = openGroupsSyncMessage;
+
+    const silent = true;
+    return this.sendIndividualProto(
+      primaryDeviceKey,
+      contentMessage,
+      Date.now(),
+      silent,
+      {} // options
+    );
+  },
+
   sendRequestContactSyncMessage(options) {
     const myNumber = textsecure.storage.user.getNumber();
     const myDevice = textsecure.storage.user.getDeviceId();
@@ -1287,6 +1319,9 @@ textsecure.MessageSender = function MessageSenderWrapper(username, password) {
   );
   this.sendContactSyncMessage = sender.sendContactSyncMessage.bind(sender);
   this.sendGroupSyncMessage = sender.sendGroupSyncMessage.bind(sender);
+  this.sendOpenGroupsSyncMessage = sender.sendOpenGroupsSyncMessage.bind(
+    sender
+  );
   this.sendRequestConfigurationSyncMessage = sender.sendRequestConfigurationSyncMessage.bind(
     sender
   );
diff --git a/protos/SignalService.proto b/protos/SignalService.proto
index f383448fe..e8f96edfe 100644
--- a/protos/SignalService.proto
+++ b/protos/SignalService.proto
@@ -314,15 +314,21 @@ message SyncMessage {
     optional bool linkPreviews                   = 4;
   }
 
-  optional Sent          sent          = 1;
-  optional Contacts      contacts      = 2;
-  optional Groups        groups        = 3;
-  optional Request       request       = 4;
-  repeated Read          read          = 5;
-  optional Blocked       blocked       = 6;
-  optional Verified      verified      = 7;
-  optional Configuration configuration = 9;
-  optional bytes         padding       = 8;
+  message OpenGroupDetails {
+    optional string url         = 1;
+    optional uint32 channelId   = 2;
+  }
+
+  optional Sent             sent             = 1;
+  optional Contacts         contacts         = 2;
+  optional Groups           groups           = 3;
+  optional Request          request          = 4;
+  repeated Read             read             = 5;
+  optional Blocked          blocked          = 6;
+  optional Verified         verified         = 7;
+  optional Configuration    configuration    = 9;
+  optional bytes            padding          = 8;
+  repeated OpenGroupDetails openGroups       = 100;
 }
 
 message AttachmentPointer {