diff --git a/lib/lock_screen.dart b/lib/lock_screen.dart
index 1a80256..d6d7ccf 100644
--- a/lib/lock_screen.dart
+++ b/lib/lock_screen.dart
@@ -257,7 +257,10 @@ class _LockScreenState extends State<LockScreen> {
           widget.showBiometricFirstController.stream.listen((_) {
             widget.biometricAuthenticate(context).then((unlocked) {
               if (unlocked) {
-                widget.onUnlocked();
+                if (widget.onUnlocked != null) {
+                  widget.onUnlocked();
+                }
+
                 Navigator.of(context).pop();
               }
             });