diff --git a/lib/features/main_screen/main_screen.dart b/lib/features/main_screen/main_screen.dart
index 30c0d718..40b3a932 100644
--- a/lib/features/main_screen/main_screen.dart
+++ b/lib/features/main_screen/main_screen.dart
@@ -104,6 +104,9 @@ class _MainScreenState extends State<MainScreen> {
 
   bool _handleGlobalKeyEvent(KeyEvent event) {
     if (event is! KeyDownEvent) return false;
+    // A dialog or sheet is on top: the screen's shortcuts must not reach
+    // through it (Ctrl+N over the welcome tour opened a second dialog, #1820).
+    if (ModalRoute.of(context)?.isCurrent == false) return false;
 
     final keyboard = HardwareKeyboard.instance;
     final shortcut = MainScreenShortcuts.resolve(
diff --git a/test/features/main_screen/sidebar_toggle_test.dart b/test/features/main_screen/sidebar_toggle_test.dart
index 9c51bd26..ad815eb9 100644
--- a/test/features/main_screen/sidebar_toggle_test.dart
+++ b/test/features/main_screen/sidebar_toggle_test.dart
@@ -1,6 +1,9 @@
-import 'package:flutter/widgets.dart';
+import 'dart:async';
 import 'dart:io';
 
+import 'package:flutter/services.dart';
+import 'package:flutter/widgets.dart';
+
 import 'package:flutter/material.dart' as material;
 import 'package:flutter_test/flutter_test.dart';
 import 'package:path_provider_platform_interface/path_provider_platform_interface.dart';
@@ -47,8 +50,7 @@ void main() {
   });
 
   group('Fluid Collapsible Sidebar (#557)', () {
-    test('AppSettings preserves sidebarVisible across sets and gets',
-        () async {
+    test('AppSettings preserves sidebarVisible across sets and gets', () async {
       expect(await AppSettings.instance.getSidebarVisible(), isTrue);
 
       await AppSettings.instance.setSidebarVisible(false);
@@ -252,6 +254,53 @@ void main() {
       );
     });
 
+    testWidgets('Ctrl+B does not reach through an open dialog (#1820)',
+        (tester) async {
+      await tester.pumpWidget(
+        queryaThemeTestShell(
+          child: const material.SizedBox(
+            width: 1200,
+            height: 800,
+            child: MainScreen(),
+          ),
+        ),
+      );
+      await tester.pumpAndSettle();
+
+      bool sidebarHidden() => find
+          .ancestor(
+            of: find.byType(ConnectionsPanel, skipOffstage: false),
+            matching: find.byWidgetPredicate(
+              (w) => w is material.Offstage && w.offstage,
+              skipOffstage: false,
+            ),
+          )
+          .evaluate()
+          .isNotEmpty;
+
+      final context = tester.element(find.byType(MainScreen));
+      unawaited(material.showDialog<void>(
+        context: context,
+        builder: (_) => const material.AlertDialog(content: Text('modal')),
+      ));
+      await tester.pumpAndSettle();
+
+      await tester.sendKeyDownEvent(LogicalKeyboardKey.controlLeft);
+      await tester.sendKeyEvent(LogicalKeyboardKey.keyB);
+      await tester.sendKeyUpEvent(LogicalKeyboardKey.controlLeft);
+      await tester.pumpAndSettle();
+      expect(sidebarHidden(), isFalse);
+
+      material.Navigator.of(context).pop();
+      await tester.pumpAndSettle();
+
+      await tester.sendKeyDownEvent(LogicalKeyboardKey.controlLeft);
+      await tester.sendKeyEvent(LogicalKeyboardKey.keyB);
+      await tester.sendKeyUpEvent(LogicalKeyboardKey.controlLeft);
+      await tester.pumpAndSettle();
+      expect(sidebarHidden(), isTrue);
+    });
+
     testWidgets(
         'isolates workspace layout constraints during sidebar spring animation (#984)',
         (tester) async {