diff --git a/packages/flutter/lib/src/services/raw_keyboard.dart b/packages/flutter/lib/src/services/raw_keyboard.dart
index 430a5484265..9fa39572b36 100644
--- a/packages/flutter/lib/src/services/raw_keyboard.dart
+++ b/packages/flutter/lib/src/services/raw_keyboard.dart
@@ -581,6 +581,11 @@ class RawKeyboard {
     // Make sure that the modifiers reflect reality, in case a modifier key was
     // pressed/released while the app didn't have focus.
     _synchronizeModifiers(event);
+    assert(event is! RawKeyDownEvent || _keysPressed.isNotEmpty,
+        'Attempted to send a key down event when no keys are in keysPressed. '
+        "This state can occur if the key event being sent doesn't properly "
+        'set its modifier flags. This was the event: $event and its data: '
+        '${event.data}');
     // Send the event to passive listeners.
     for (final ValueChanged<RawKeyEvent> listener in List<ValueChanged<RawKeyEvent>>.from(_listeners)) {
       if (_listeners.contains(listener)) {
diff --git a/packages/flutter/lib/src/widgets/shortcuts.dart b/packages/flutter/lib/src/widgets/shortcuts.dart
index 2b534051d1d..09e5447f12f 100644
--- a/packages/flutter/lib/src/widgets/shortcuts.dart
+++ b/packages/flutter/lib/src/widgets/shortcuts.dart
@@ -306,7 +306,21 @@ class ShortcutManager extends ChangeNotifier with Diagnosticable {
       return false;
     }
     assert(context != null);
-    final LogicalKeySet keySet = keysPressed ?? LogicalKeySet.fromSet(RawKeyboard.instance.keysPressed);
+    LogicalKeySet keySet = keysPressed;
+    if (keySet == null) {
+      assert(RawKeyboard.instance.keysPressed.isNotEmpty,
+        'Received a key down event when no keys are in keysPressed. '
+        "This state can occur if the key event being sent doesn't properly "
+        'set its modifier flags. This was the event: $event and its data: '
+        '${event.data}');
+      // Avoid the crash in release mode, since it's easy to miss a particular
+      // bad key sequence in testing, and so shouldn't crash the app in release.
+      if (RawKeyboard.instance.keysPressed.isNotEmpty) {
+        keySet = LogicalKeySet.fromSet(RawKeyboard.instance.keysPressed);
+      } else {
+        return false;
+      }
+    }
     Intent matchedIntent = _shortcuts[keySet];
     if (matchedIntent == null) {
       // If there's not a more specific match, We also look for any keys that
diff --git a/packages/flutter/test/services/raw_keyboard_test.dart b/packages/flutter/test/services/raw_keyboard_test.dart
index b77e99f9bea..14197cc9dab 100644
--- a/packages/flutter/test/services/raw_keyboard_test.dart
+++ b/packages/flutter/test/services/raw_keyboard_test.dart
@@ -4,6 +4,7 @@
 
 // @dart = 2.8
 
+import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
@@ -277,6 +278,36 @@ void main() {
         ),
       );
     });
+
+    testWidgets('RawKeyboard asserts if no keys are in keysPressed after receiving a key down event', (WidgetTester tester) async {
+      FlutterErrorDetails errorDetails;
+      final FlutterExceptionHandler oldHandler = FlutterError.onError;
+      FlutterError.onError = (FlutterErrorDetails details) {
+        errorDetails = details;
+      };
+      try {
+        await ServicesBinding.instance.defaultBinaryMessenger
+            .handlePlatformMessage(
+          SystemChannels.keyEvent.name,
+          SystemChannels.keyEvent.codec.encodeMessage(const <String, dynamic>{
+            'type': 'keydown',
+            'keymap': 'android',
+            'keyCode': 0x3b, // Left shift key keyCode
+            'scanCode': 0x2a,
+            'metaState': 0x0, // No shift key metaState set!
+            'source': 0x101,
+            'deviceId': 1,
+          }),
+              (ByteData data) {},
+        );
+      } finally {
+        FlutterError.onError = oldHandler;
+      }
+      expect(errorDetails, isNotNull);
+      expect(errorDetails.stack, isNotNull);
+      final String fullErrorMessage = errorDetails.toString().replaceAll('\n', ' ');
+      expect(fullErrorMessage, contains('Attempted to send a key down event when no keys are in keysPressed'));
+    });
   });
 
   group('RawKeyEventDataAndroid', () {