diff --git a/lib/model/indexsender.go b/lib/model/indexsender.go
index 723312615..6ebe77164 100644
--- a/lib/model/indexsender.go
+++ b/lib/model/indexsender.go
@@ -242,12 +242,6 @@ func (r *indexSenderRegistry) add(folder config.FolderConfiguration, fset *db.Fi
 	r.mut.Unlock()
 }
 
-func (r *indexSenderRegistry) addNew(folder config.FolderConfiguration, fset *db.FileSet) {
-	r.mut.Lock()
-	r.startLocked(folder.ID, fset, 0)
-	r.mut.Unlock()
-}
-
 func (r *indexSenderRegistry) addLocked(folder config.FolderConfiguration, fset *db.FileSet, startInfo *indexSenderStartInfo) {
 	myIndexID := fset.IndexID(protocol.LocalDeviceID)
 	mySequence := fset.Sequence(protocol.LocalDeviceID)
@@ -282,7 +276,7 @@ func (r *indexSenderRegistry) addLocked(folder config.FolderConfiguration, fset
 		l.Infof("Device %v folder %s has mismatching index ID for us (%v != %v)", r.deviceID, folder.Description(), startInfo.local.IndexID, myIndexID)
 		startSequence = 0
 	} else {
-		l.Debugf("Device %v folder %s is not delta index compatible", r.deviceID, folder.Description())
+		l.Debugf("Device %v folder %s has no index ID for us", r.deviceID, folder.Description())
 	}
 
 	// This is the other side's description of themselves. We
@@ -296,6 +290,7 @@ func (r *indexSenderRegistry) addLocked(folder config.FolderConfiguration, fset
 		// do not support delta indexes and we should clear any
 		// information we have from them before accepting their
 		// index, which will presumably be a full index.
+		l.Debugf("Device %v folder %s does not announce an index ID", r.deviceID, folder.Description())
 		fset.Drop(r.deviceID)
 	} else if startInfo.remote.IndexID != theirIndexID {
 		// The index ID we have on file is not what they're
@@ -308,22 +303,18 @@ func (r *indexSenderRegistry) addLocked(folder config.FolderConfiguration, fset
 		fset.SetIndexID(r.deviceID, startInfo.remote.IndexID)
 	}
 
-	r.startLocked(folder.ID, fset, startSequence)
-}
-
-func (r *indexSenderRegistry) startLocked(folderID string, fset *db.FileSet, startSequence int64) {
-	if is, ok := r.indexSenders[folderID]; ok {
+	if is, ok := r.indexSenders[folder.ID]; ok {
 		r.sup.RemoveAndWait(is.token, 0)
-		delete(r.indexSenders, folderID)
+		delete(r.indexSenders, folder.ID)
 	}
-	if _, ok := r.startInfos[folderID]; ok {
-		delete(r.startInfos, folderID)
+	if _, ok := r.startInfos[folder.ID]; ok {
+		delete(r.startInfos, folder.ID)
 	}
 
 	is := &indexSender{
 		conn:         r.conn,
 		connClosed:   r.closed,
-		folder:       folderID,
+		folder:       folder.ID,
 		fset:         fset,
 		prevSequence: startSequence,
 		evLogger:     r.evLogger,
@@ -331,13 +322,13 @@ func (r *indexSenderRegistry) startLocked(folderID string, fset *db.FileSet, sta
 		resumeChan:   make(chan *db.FileSet),
 	}
 	is.token = r.sup.Add(is)
-	r.indexSenders[folderID] = is
+	r.indexSenders[folder.ID] = is
 }
 
-// addPaused stores the given info to start an index sender once resume is called
+// addPending stores the given info to start an index sender once resume is called
 // for this folder.
 // If an index sender is already running, it will be stopped.
-func (r *indexSenderRegistry) addPaused(folder config.FolderConfiguration, startInfo *indexSenderStartInfo) {
+func (r *indexSenderRegistry) addPending(folder config.FolderConfiguration, startInfo *indexSenderStartInfo) {
 	r.mut.Lock()
 	defer r.mut.Unlock()
 
diff --git a/lib/model/model.go b/lib/model/model.go
index d1769584b..deb05e177 100644
--- a/lib/model/model.go
+++ b/lib/model/model.go
@@ -254,13 +254,16 @@ func NewModel(cfg config.Wrapper, id protocol.DeviceID, clientName, clientVersio
 func (m *model) serve(ctx context.Context) error {
 	// Add and start folders
 	cacheIgnoredFiles := m.cfg.Options().CacheIgnoredFiles
+	clusterConfigDevices := make(deviceIDSet, len(m.cfg.Devices()))
 	for _, folderCfg := range m.cfg.Folders() {
 		if folderCfg.Paused {
 			folderCfg.CreateRoot()
 			continue
 		}
 		m.newFolder(folderCfg, cacheIgnoredFiles)
+		clusterConfigDevices.add(folderCfg.DeviceIDs())
 	}
+	m.resendClusterConfig(clusterConfigDevices.AsSlice())
 	m.cfg.Subscribe(m)
 
 	close(m.started)
@@ -519,13 +522,9 @@ func (m *model) restartFolder(from, to config.FolderConfiguration, cacheIgnoredF
 		// In case the folder was newly shared with us we already got a
 		// cluster config and wont necessarily get another soon - start
 		// sending indexes if connected.
-		isNew := !from.SharedWith(indexSenders.deviceID)
-		if isNew {
-			indexSenders.addNew(to, fset)
-		}
 		if to.Paused {
 			indexSenders.pause(to.ID)
-		} else if !isNew && (fsetNil || from.Paused) {
+		} else if !from.SharedWith(indexSenders.deviceID) || fsetNil || from.Paused {
 			indexSenders.resume(to, fset)
 		}
 	}
@@ -554,20 +553,10 @@ func (m *model) newFolder(cfg config.FolderConfiguration, cacheIgnoredFiles bool
 	// Cluster configs might be received and processed before reaching this
 	// point, i.e. before the folder is started. If that's the case, start
 	// index senders here.
-	localSequenceZero := fset.Sequence(protocol.LocalDeviceID) == 0
 	m.pmut.RLock()
 	for _, id := range cfg.DeviceIDs() {
 		if is, ok := m.indexSenders[id]; ok {
-			if localSequenceZero && fset.Sequence(id) == 0 {
-				// In case this folder was shared to us and
-				// newly added, add a new index sender.
-				is.addNew(cfg, fset)
-			} else {
-				// For existing folders we stored the index data from
-				// the cluster config, so resume based on that - if
-				// we didn't get a cluster config yet, it's a noop.
-				is.resume(cfg, fset)
-			}
+			is.resume(cfg, fset)
 		}
 	}
 	m.pmut.RUnlock()
@@ -1175,6 +1164,7 @@ func (m *model) ccHandleFolders(folders []protocol.Folder, deviceCfg config.Devi
 				continue
 			}
 			m.cfg.AddOrUpdatePendingFolder(folder.ID, folder.Label, deviceID)
+			indexSenders.addPending(cfg, ccDeviceInfos[folder.ID])
 			changed = true
 			m.evLogger.Log(events.FolderRejected, map[string]string{
 				"folder":      folder.ID,
@@ -1192,7 +1182,7 @@ func (m *model) ccHandleFolders(folders []protocol.Folder, deviceCfg config.Devi
 		}
 
 		if cfg.Paused {
-			indexSenders.addPaused(cfg, ccDeviceInfos[folder.ID])
+			indexSenders.addPending(cfg, ccDeviceInfos[folder.ID])
 			continue
 		}
 
@@ -1234,7 +1224,7 @@ func (m *model) ccHandleFolders(folders []protocol.Folder, deviceCfg config.Devi
 			// Shouldn't happen because !cfg.Paused, but might happen
 			// if the folder is about to be unpaused, but not yet.
 			l.Debugln("ccH: no fset", folder.ID)
-			indexSenders.addPaused(cfg, ccDeviceInfos[folder.ID])
+			indexSenders.addPending(cfg, ccDeviceInfos[folder.ID])
 			continue
 		}
 
@@ -2482,7 +2472,7 @@ func (m *model) CommitConfiguration(from, to config.Configuration) bool {
 	// Go through the folder configs and figure out if we need to restart or not.
 
 	// Tracks devices affected by any configuration change to resend ClusterConfig.
-	clusterConfigDevices := make(map[protocol.DeviceID]struct{}, len(from.Devices)+len(to.Devices))
+	clusterConfigDevices := make(deviceIDSet, len(from.Devices)+len(to.Devices))
 
 	fromFolders := mapFolders(from.Folders)
 	toFolders := mapFolders(to.Folders)
@@ -2495,7 +2485,7 @@ func (m *model) CommitConfiguration(from, to config.Configuration) bool {
 				l.Infoln("Adding folder", cfg.Description())
 				m.newFolder(cfg, to.Options.CacheIgnoredFiles)
 			}
-			clusterConfigDevices = addDeviceIDsToMap(clusterConfigDevices, cfg.DeviceIDs())
+			clusterConfigDevices.add(cfg.DeviceIDs())
 		}
 	}
 
@@ -2504,7 +2494,7 @@ func (m *model) CommitConfiguration(from, to config.Configuration) bool {
 		if !ok {
 			// The folder was removed.
 			m.removeFolder(fromCfg)
-			clusterConfigDevices = addDeviceIDsToMap(clusterConfigDevices, fromCfg.DeviceIDs())
+			clusterConfigDevices.add(fromCfg.DeviceIDs())
 			continue
 		}
 
@@ -2516,8 +2506,8 @@ func (m *model) CommitConfiguration(from, to config.Configuration) bool {
 		// Check if anything differs that requires a restart.
 		if !reflect.DeepEqual(fromCfg.RequiresRestartOnly(), toCfg.RequiresRestartOnly()) || from.Options.CacheIgnoredFiles != to.Options.CacheIgnoredFiles {
 			m.restartFolder(fromCfg, toCfg, to.Options.CacheIgnoredFiles)
-			clusterConfigDevices = addDeviceIDsToMap(clusterConfigDevices, fromCfg.DeviceIDs())
-			clusterConfigDevices = addDeviceIDsToMap(clusterConfigDevices, toCfg.DeviceIDs())
+			clusterConfigDevices.add(fromCfg.DeviceIDs())
+			clusterConfigDevices.add(toCfg.DeviceIDs())
 		}
 
 		// Emit the folder pause/resume event
@@ -2591,11 +2581,7 @@ func (m *model) CommitConfiguration(from, to config.Configuration) bool {
 	}
 	m.pmut.RUnlock()
 	// Generating cluster-configs acquires fmut -> must happen outside of pmut.
-	ids := make([]protocol.DeviceID, 0, len(clusterConfigDevices))
-	for id := range clusterConfigDevices {
-		ids = append(ids, id)
-	}
-	m.resendClusterConfig(ids)
+	m.resendClusterConfig(clusterConfigDevices.AsSlice())
 
 	m.globalRequestLimiter.setCapacity(1024 * to.Options.MaxConcurrentIncomingRequestKiB())
 	m.folderIOLimiter.setCapacity(to.Options.MaxFolderConcurrency())
@@ -2801,13 +2787,22 @@ func sanitizePath(path string) string {
 	return strings.TrimSpace(b.String())
 }
 
-func addDeviceIDsToMap(m map[protocol.DeviceID]struct{}, s []protocol.DeviceID) map[protocol.DeviceID]struct{} {
-	for _, id := range s {
-		if _, ok := m[id]; !ok {
-			m[id] = struct{}{}
+type deviceIDSet map[protocol.DeviceID]struct{}
+
+func (s deviceIDSet) add(ids []protocol.DeviceID) {
+	for _, id := range ids {
+		if _, ok := s[id]; !ok {
+			s[id] = struct{}{}
 		}
 	}
-	return m
+}
+
+func (s deviceIDSet) AsSlice() []protocol.DeviceID {
+	ids := make([]protocol.DeviceID, 0, len(s))
+	for id := range s {
+		ids = append(ids, id)
+	}
+	return ids
 }
 
 func encryptionTokenPath(cfg config.FolderConfiguration) string {
diff --git a/lib/model/requests_test.go b/lib/model/requests_test.go
index a2b7db5e6..58e2171a4 100644
--- a/lib/model/requests_test.go
+++ b/lib/model/requests_test.go
@@ -1275,9 +1275,6 @@ func TestRequestIndexSenderPause(t *testing.T) {
 }
 
 func TestRequestIndexSenderClusterConfigBeforeStart(t *testing.T) {
-	done := make(chan struct{})
-	defer close(done)
-
 	ldb := db.NewLowlevel(backend.OpenMemory())
 	w, fcfg := tmpDefaultWrapper()
 	tfs := fcfg.Filesystem()
@@ -1294,11 +1291,14 @@ func TestRequestIndexSenderClusterConfigBeforeStart(t *testing.T) {
 	m.evCancel()
 	<-m.stopped
 
-	// Add connection (sends cluster config) before starting the new model
+	// Add connection (sends incoming cluster config) before starting the new model
 	m = newModel(w, myID, "syncthing", "dev", ldb, nil)
 	defer cleanupModel(m)
 	fc := addFakeConn(m, device1)
-	indexChan := make(chan []protocol.FileInfo)
+	done := make(chan struct{})
+	defer close(done) // Must be the last thing to be deferred, thus first to run.
+	indexChan := make(chan []protocol.FileInfo, 1)
+	ccChan := make(chan protocol.ClusterConfig, 1)
 	fc.mut.Lock()
 	fc.indexFn = func(_ context.Context, folder string, fs []protocol.FileInfo) {
 		select {
@@ -1306,16 +1306,30 @@ func TestRequestIndexSenderClusterConfigBeforeStart(t *testing.T) {
 		case <-done:
 		}
 	}
+	fc.clusterConfigFn = func(cc protocol.ClusterConfig) {
+		select {
+		case ccChan <- cc:
+		case <-done:
+		}
+	}
 	fc.mut.Unlock()
 
 	m.ServeBackground()
-	<-m.started
+
+	timeout := time.After(5 * time.Second)
+
+	// Check that cluster-config is resent after adding folders when starting model
+	select {
+	case <-timeout:
+		t.Fatal("timed out before receiving cluster-config")
+	case <-ccChan:
+	}
 
 	// Check that an index is sent for the newly added item
 	must(t, tfs.Mkdir(dir2, 0777))
 	m.ScanFolders()
 	select {
-	case <-time.After(5 * time.Second):
+	case <-timeout:
 		t.Fatal("timed out before receiving index")
 	case <-indexChan:
 	}