diff --git a/lib/l10n/app_en.arb b/lib/l10n/app_en.arb
index 34e89c5..3c755fa 100644
--- a/lib/l10n/app_en.arb
+++ b/lib/l10n/app_en.arb
@@ -8,6 +8,7 @@
   "locationButton": "Send location",
   "statusButton": "Show status",
   "settingsButton": "Change settings",
+  "invalidValue": "Invalid value",
   "idLabel": "Device identifier",
   "urlLabel": "Server URL",
   "accuracyLabel": "Location accuracy",
diff --git a/lib/settings_screen.dart b/lib/settings_screen.dart
index 750afae..af1c184 100644
--- a/lib/settings_screen.dart
+++ b/lib/settings_screen.dart
@@ -43,6 +43,8 @@ class _SettingsScreenState extends State<SettingsScreen> {
         : Preferences.instance.getString(key) ?? '';
 
     final controller = TextEditingController(text: initialValue);
+    final scaffoldManager = ScaffoldMessenger.of(context);
+    final errorMessage = AppLocalizations.of(context)!.invalidValue;
 
     final result = await showDialog<String>(
       context: context,
@@ -67,6 +69,13 @@ class _SettingsScreenState extends State<SettingsScreen> {
     );
 
     if (result != null && result.isNotEmpty) {
+      if (key == Preferences.url) {
+        final uri = Uri.tryParse(result);
+        if (uri == null || uri.host.isEmpty || !(uri.scheme == 'http' || uri.scheme == 'https')) {
+          scaffoldManager.showSnackBar(SnackBar(content: Text(errorMessage)));
+          return;
+        }
+      }
       if (isInt) {
         final intValue = int.tryParse(result);
         if (intValue != null) {