diff --git a/widget/windows/KeyboardLayout.cpp b/widget/windows/KeyboardLayout.cpp
index 0b19ff598fdb..66bc76c57287 100644
--- a/widget/windows/KeyboardLayout.cpp
+++ b/widget/windows/KeyboardLayout.cpp
@@ -2285,8 +2285,8 @@ KeyboardLayout::SynthesizeNativeKeyEvent(nsWindowBase* aWidget,
     }
     ::SetKeyboardState(kbdState);
     ModifierKeyState modKeyState;
-    UINT scanCode = ComputeScanCodeForVirtualKeyCode(
-      argumentKeySpecific ? argumentKeySpecific : aNativeKeyCode);
+    UINT scanCode =
+      ComputeScanCodeForVirtualKeyCode(keySpecific ? keySpecific : key);
     LPARAM lParam = static_cast<LPARAM>(scanCode << 16);
     // Add extended key flag to the lParam for right control key and right alt
     // key.
@@ -2340,8 +2340,8 @@ KeyboardLayout::SynthesizeNativeKeyEvent(nsWindowBase* aWidget,
     }
     ::SetKeyboardState(kbdState);
     ModifierKeyState modKeyState;
-    UINT scanCode = ComputeScanCodeForVirtualKeyCode(
-      argumentKeySpecific ? argumentKeySpecific : aNativeKeyCode);
+    UINT scanCode =
+      ComputeScanCodeForVirtualKeyCode(keySpecific ? keySpecific : key);
     LPARAM lParam = static_cast<LPARAM>(scanCode << 16);
     // Add extended key flag to the lParam for right control key and right alt
     // key.
diff --git a/widget/windows/KeyboardLayout.h b/widget/windows/KeyboardLayout.h
index 429f26f443e0..17825ff92dc4 100644
--- a/widget/windows/KeyboardLayout.h
+++ b/widget/windows/KeyboardLayout.h
@@ -304,7 +304,7 @@ public:
       msg.hwnd = aWnd;
       msg.message = mIsDeadKey ? WM_DEADCHAR : WM_CHAR;
       msg.wParam = static_cast<WPARAM>(mCharCode);
-      msg.lParam = static_cast<LPARAM>(mScanCode);
+      msg.lParam = static_cast<LPARAM>(mScanCode << 16);
       msg.time = 0;
       msg.pt.x = msg.pt.y = 0;
       return msg;