diff --git a/user/manager.go b/user/manager.go
index 34d96403..79fbe26b 100644
--- a/user/manager.go
+++ b/user/manager.go
@@ -639,6 +639,13 @@ func (a *Manager) Authorize(user *User, topic string, perm Permission) error {
 	if user != nil && user.Role == RoleAdmin {
 		return nil // Admin can do everything
 	}
+	// A user always has full access to their own sync topic, which the apps use
+	// to sync subscriptions/settings across devices. Without this, an
+	// auth-default-access of "deny-all" locks the user out of their own sync
+	// topic (no ACL entry is created for it at user creation). See #733.
+	if user != nil && user.SyncTopic != "" && topic == user.SyncTopic {
+		return nil
+	}
 	username := Everyone
 	if user != nil {
 		username = user.Name
diff --git a/user/manager_test.go b/user/manager_test.go
index 6d13929e..6e5a6a05 100644
--- a/user/manager_test.go
+++ b/user/manager_test.go
@@ -129,6 +129,13 @@ func TestManager_FullScenario_Default_DenyAll(t *testing.T) {
 		require.Nil(t, a.Authorize(ben, "announcements", PermissionRead))
 		require.Equal(t, ErrUnauthorized, a.Authorize(ben, "announcements", PermissionWrite))
 
+		// User has full access to their own sync topic, even under deny-all,
+		// but not to another user's sync topic (#733)
+		require.Nil(t, a.Authorize(ben, ben.SyncTopic, PermissionRead))
+		require.Nil(t, a.Authorize(ben, ben.SyncTopic, PermissionWrite))
+		require.Equal(t, ErrUnauthorized, a.Authorize(ben, john.SyncTopic, PermissionRead))
+		require.Equal(t, ErrUnauthorized, a.Authorize(ben, john.SyncTopic, PermissionWrite))
+
 		// User john should have
 		//  "deny" to mytopic_deny*,
 		//    "ro" to mytopic_ro*,