diff --git a/cmd/syncthing/gui.go b/cmd/syncthing/gui.go
index 8503158db..64c1c3401 100644
--- a/cmd/syncthing/gui.go
+++ b/cmd/syncthing/gui.go
@@ -41,8 +41,7 @@ import (
 )
 
 var (
-	configInSync = true
-	startTime    = time.Now()
+	startTime = time.Now()
 )
 
 type apiService struct {
@@ -100,12 +99,13 @@ type configIntf interface {
 	GUI() config.GUIConfiguration
 	Raw() config.Configuration
 	Options() config.OptionsConfiguration
-	Replace(cfg config.Configuration) config.CommitResponse
+	Replace(cfg config.Configuration) error
 	Subscribe(c config.Committer)
 	Folders() map[string]config.FolderConfiguration
 	Devices() map[protocol.DeviceID]config.DeviceConfiguration
 	Save() error
 	ListenAddresses() []string
+	RequiresRestart() bool
 }
 
 type connectionsIntf interface {
@@ -722,13 +722,19 @@ func (s *apiService) postSystemConfig(w http.ResponseWriter, r *http.Request) {
 
 	// Activate and save
 
-	resp := s.cfg.Replace(to)
-	configInSync = !resp.RequiresRestart
-	s.cfg.Save()
+	if err := s.cfg.Replace(to); err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+
+	if err := s.cfg.Save(); err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
 }
 
 func (s *apiService) getSystemConfigInsync(w http.ResponseWriter, r *http.Request) {
-	sendJSON(w, map[string]bool{"configInSync": configInSync})
+	sendJSON(w, map[string]bool{"configInSync": !s.cfg.RequiresRestart()})
 }
 
 func (s *apiService) postSystemRestart(w http.ResponseWriter, r *http.Request) {
diff --git a/cmd/syncthing/mocked_config_test.go b/cmd/syncthing/mocked_config_test.go
index d4e734a73..55686f51f 100644
--- a/cmd/syncthing/mocked_config_test.go
+++ b/cmd/syncthing/mocked_config_test.go
@@ -31,8 +31,8 @@ func (c *mockedConfig) Options() config.OptionsConfiguration {
 	return config.OptionsConfiguration{}
 }
 
-func (c *mockedConfig) Replace(cfg config.Configuration) config.CommitResponse {
-	return config.CommitResponse{}
+func (c *mockedConfig) Replace(cfg config.Configuration) error {
+	return nil
 }
 
 func (c *mockedConfig) Subscribe(cm config.Committer) {}
@@ -48,3 +48,7 @@ func (c *mockedConfig) Devices() map[protocol.DeviceID]config.DeviceConfiguratio
 func (c *mockedConfig) Save() error {
 	return nil
 }
+
+func (c *mockedConfig) RequiresRestart() bool {
+	return false
+}
diff --git a/lib/config/commit_test.go b/lib/config/commit_test.go
index 3cff5cd04..759834647 100644
--- a/lib/config/commit_test.go
+++ b/lib/config/commit_test.go
@@ -11,12 +11,18 @@ import (
 	"testing"
 )
 
-type requiresRestart struct{}
+type requiresRestart struct {
+	committed chan struct{}
+}
 
 func (requiresRestart) VerifyConfiguration(_, _ Configuration) error {
 	return nil
 }
-func (requiresRestart) CommitConfiguration(_, _ Configuration) bool {
+func (c requiresRestart) CommitConfiguration(_, _ Configuration) bool {
+	select {
+	case c.committed <- struct{}{}:
+	default:
+	}
 	return false
 }
 func (requiresRestart) String() string {
@@ -28,7 +34,7 @@ type validationError struct{}
 func (validationError) VerifyConfiguration(_, _ Configuration) error {
 	return errors.New("some error")
 }
-func (validationError) CommitConfiguration(_, _ Configuration) bool {
+func (c validationError) CommitConfiguration(_, _ Configuration) bool {
 	return true
 }
 func (validationError) String() string {
@@ -44,11 +50,11 @@ func TestReplaceCommit(t *testing.T) {
 	// Replace config. We should get back a clean response and the config
 	// should change.
 
-	resp := w.Replace(Configuration{Version: 1})
-	if resp.ValidationError != nil {
-		t.Fatal("Should not have a validation error")
+	err := w.Replace(Configuration{Version: 1})
+	if err != nil {
+		t.Fatal("Should not have a validation error:", err)
 	}
-	if resp.RequiresRestart {
+	if w.RequiresRestart() {
 		t.Fatal("Should not require restart")
 	}
 	if w.Raw().Version != 1 {
@@ -58,13 +64,16 @@ func TestReplaceCommit(t *testing.T) {
 	// Now with a subscriber requiring restart. We should get a clean response
 	// but with the restart flag set, and the config should change.
 
-	w.Subscribe(requiresRestart{})
+	sub0 := requiresRestart{committed: make(chan struct{}, 1)}
+	w.Subscribe(sub0)
 
-	resp = w.Replace(Configuration{Version: 2})
-	if resp.ValidationError != nil {
-		t.Fatal("Should not have a validation error")
+	err = w.Replace(Configuration{Version: 2})
+	if err != nil {
+		t.Fatal("Should not have a validation error:", err)
 	}
-	if !resp.RequiresRestart {
+
+	<-sub0.committed
+	if !w.RequiresRestart() {
 		t.Fatal("Should require restart")
 	}
 	if w.Raw().Version != 2 {
@@ -76,12 +85,12 @@ func TestReplaceCommit(t *testing.T) {
 
 	w.Subscribe(validationError{})
 
-	resp = w.Replace(Configuration{Version: 3})
-	if resp.ValidationError == nil {
+	err = w.Replace(Configuration{Version: 3})
+	if err == nil {
 		t.Fatal("Should have a validation error")
 	}
-	if resp.RequiresRestart {
-		t.Fatal("Should not require restart")
+	if !w.RequiresRestart() {
+		t.Fatal("Should still require restart")
 	}
 	if w.Raw().Version != 2 {
 		t.Fatal("Config should not have changed")
diff --git a/lib/config/wrapper.go b/lib/config/wrapper.go
index 212a70af8..a848849cd 100644
--- a/lib/config/wrapper.go
+++ b/lib/config/wrapper.go
@@ -8,6 +8,7 @@ package config
 
 import (
 	"os"
+	"sync/atomic"
 
 	"github.com/syncthing/syncthing/lib/events"
 	"github.com/syncthing/syncthing/lib/osutil"
@@ -41,11 +42,6 @@ type Committer interface {
 	String() string
 }
 
-type CommitResponse struct {
-	ValidationError error
-	RequiresRestart bool
-}
-
 // A wrapper around a Configuration that manages loads, saves and published
 // notifications of changes to registered Handlers
 
@@ -58,6 +54,8 @@ type Wrapper struct {
 	replaces  chan Configuration
 	subs      []Committer
 	mut       sync.Mutex
+
+	requiresRestart uint32 // an atomic bool
 }
 
 // Wrap wraps an existing Configuration structure and ties it to a file on
@@ -128,32 +126,21 @@ func (w *Wrapper) Raw() Configuration {
 }
 
 // Replace swaps the current configuration object for the given one.
-func (w *Wrapper) Replace(cfg Configuration) CommitResponse {
+func (w *Wrapper) Replace(cfg Configuration) error {
 	w.mut.Lock()
 	defer w.mut.Unlock()
+
 	return w.replaceLocked(cfg)
 }
 
-func (w *Wrapper) replaceLocked(to Configuration) CommitResponse {
+func (w *Wrapper) replaceLocked(to Configuration) error {
 	from := w.cfg
 
 	for _, sub := range w.subs {
 		l.Debugln(sub, "verifying configuration")
 		if err := sub.VerifyConfiguration(from, to); err != nil {
 			l.Debugln(sub, "rejected config:", err)
-			return CommitResponse{
-				ValidationError: err,
-			}
-		}
-	}
-
-	allOk := true
-	for _, sub := range w.subs {
-		l.Debugln(sub, "committing configuration")
-		ok := sub.CommitConfiguration(from, to)
-		if !ok {
-			l.Debugln(sub, "requires restart")
-			allOk = false
+			return err
 		}
 	}
 
@@ -161,8 +148,22 @@ func (w *Wrapper) replaceLocked(to Configuration) CommitResponse {
 	w.deviceMap = nil
 	w.folderMap = nil
 
-	return CommitResponse{
-		RequiresRestart: !allOk,
+	w.notifyListeners(from, to)
+
+	return nil
+}
+
+func (w *Wrapper) notifyListeners(from, to Configuration) {
+	for _, sub := range w.subs {
+		go w.notifyListener(sub, from, to)
+	}
+}
+
+func (w *Wrapper) notifyListener(sub Committer, from, to Configuration) {
+	l.Debugln(sub, "committing configuration")
+	if !sub.CommitConfiguration(from, to) {
+		l.Debugln(sub, "requires restart")
+		w.setRequiresRestart()
 	}
 }
 
@@ -182,7 +183,7 @@ func (w *Wrapper) Devices() map[protocol.DeviceID]DeviceConfiguration {
 
 // SetDevice adds a new device to the configuration, or overwrites an existing
 // device with the same ID.
-func (w *Wrapper) SetDevice(dev DeviceConfiguration) CommitResponse {
+func (w *Wrapper) SetDevice(dev DeviceConfiguration) error {
 	w.mut.Lock()
 	defer w.mut.Unlock()
 
@@ -218,7 +219,7 @@ func (w *Wrapper) Folders() map[string]FolderConfiguration {
 
 // SetFolder adds a new folder to the configuration, or overwrites an existing
 // folder with the same ID.
-func (w *Wrapper) SetFolder(fld FolderConfiguration) CommitResponse {
+func (w *Wrapper) SetFolder(fld FolderConfiguration) error {
 	w.mut.Lock()
 	defer w.mut.Unlock()
 
@@ -246,7 +247,7 @@ func (w *Wrapper) Options() OptionsConfiguration {
 }
 
 // SetOptions replaces the current options configuration object.
-func (w *Wrapper) SetOptions(opts OptionsConfiguration) CommitResponse {
+func (w *Wrapper) SetOptions(opts OptionsConfiguration) error {
 	w.mut.Lock()
 	defer w.mut.Unlock()
 	newCfg := w.cfg.Copy()
@@ -262,7 +263,7 @@ func (w *Wrapper) GUI() GUIConfiguration {
 }
 
 // SetGUI replaces the current GUI configuration object.
-func (w *Wrapper) SetGUI(gui GUIConfiguration) CommitResponse {
+func (w *Wrapper) SetGUI(gui GUIConfiguration) error {
 	w.mut.Lock()
 	defer w.mut.Unlock()
 	newCfg := w.cfg.Copy()
@@ -332,3 +333,11 @@ func (w *Wrapper) ListenAddresses() []string {
 	}
 	return util.UniqueStrings(addresses)
 }
+
+func (w *Wrapper) RequiresRestart() bool {
+	return atomic.LoadUint32(&w.requiresRestart) != 0
+}
+
+func (w *Wrapper) setRequiresRestart() {
+	atomic.StoreUint32(&w.requiresRestart, 1)
+}