diff --git a/lib/ui/dialogs/single_input_dialog.dart b/lib/ui/dialogs/single_input_dialog.dart
index 8359658..9641d8b 100644
--- a/lib/ui/dialogs/single_input_dialog.dart
+++ b/lib/ui/dialogs/single_input_dialog.dart
@@ -35,8 +35,8 @@ class __InputURLDialogState extends State<SingleInputDialog> {
   TextEditingController _controller;
 
   bool get _isValid =>
-      (_controller.text.isNotEmpty || widget.canBeEmpty) &&
-      widget.checkInput(_controller.text);
+      (_controller.text.isEmpty && widget.canBeEmpty) ||
+      (_controller.text.isNotEmpty && widget.checkInput(_controller.text));
 
   @override
   void initState() {