diff --git a/engine/src/flutter/shell/platform/darwin/macos/framework/Source/FlutterChannelKeyResponder.mm b/engine/src/flutter/shell/platform/darwin/macos/framework/Source/FlutterChannelKeyResponder.mm
index 392986e0d01..0f59f61bfb7 100644
--- a/engine/src/flutter/shell/platform/darwin/macos/framework/Source/FlutterChannelKeyResponder.mm
+++ b/engine/src/flutter/shell/platform/darwin/macos/framework/Source/FlutterChannelKeyResponder.mm
@@ -50,8 +50,12 @@
     case NSEventTypeFlagsChanged:
       if (event.modifierFlags < _previouslyPressedFlags) {
         type = @"keyup";
-      } else {
+      } else if (event.modifierFlags > _previouslyPressedFlags) {
         type = @"keydown";
+      } else {
+        // ignore duplicate modifiers; This can happen in situations like switching
+        // between application windows when MacOS only sends the up event to new window.
+        return;
       }
       break;
     default:
diff --git a/engine/src/flutter/shell/platform/darwin/macos/framework/Source/FlutterChannelKeyResponderUnittests.mm b/engine/src/flutter/shell/platform/darwin/macos/framework/Source/FlutterChannelKeyResponderUnittests.mm
index 0ee7445efec..01254d6b7c7 100644
--- a/engine/src/flutter/shell/platform/darwin/macos/framework/Source/FlutterChannelKeyResponderUnittests.mm
+++ b/engine/src/flutter/shell/platform/darwin/macos/framework/Source/FlutterChannelKeyResponderUnittests.mm
@@ -170,6 +170,16 @@ TEST(FlutterChannelKeyResponderUnittests, BasicKeyEvent) {
 
   [messages removeAllObjects];
   [responses removeAllObjects];
+
+  // RShift up again, should be ignored and not produce a keydown event.
+  next_response = false;
+  [responder handleEvent:keyEvent(NSEventTypeFlagsChanged, 0x100, @"", @"", FALSE, 60)
+                callback:^(BOOL handled) {
+                  [responses addObject:@(handled)];
+                }];
+
+  EXPECT_EQ([messages count], 0u);
+  EXPECT_EQ([responses count], 0u);
 }
 
 TEST(FlutterChannelKeyResponderUnittests, EmptyResponseIsTakenAsHandled) {