--- a/widget/cocoa/TextInputHandler.h
+++ b/widget/cocoa/TextInputHandler.h
@@ -272,18 +272,21 @@ public:
    * @param aNativeKeyCode        A native keycode.
    */
   static KeyNameIndex ComputeGeckoKeyNameIndex(UInt32 aNativeKeyCode);
 
   /**
    * ComputeGeckoCodeNameIndex() returns Gecko code name index for the key.
    *
    * @param aNativeKeyCode        A native keycode.
+   * @param aKbType               A native Keyboard Type value.  Typically,
+   *                              this is a result of ::LMGetKbdType().
    */
-  static CodeNameIndex ComputeGeckoCodeNameIndex(UInt32 aNativeKeyCode);
+  static CodeNameIndex ComputeGeckoCodeNameIndex(UInt32 aNativeKeyCode,
+                                                 UInt32 aKbType);
 
 protected:
   /**
    * TranslateToString() computes the inputted text from the native keyCode,
    * modifier flags and keyboard type.
    *
    * @param aKeyCode              A native keyCode.
    * @param aModifiers            Combination of native modifier flags.

--- a/widget/cocoa/TextInputHandler.mm
+++ b/widget/cocoa/TextInputHandler.mm
@@ -1025,17 +1025,17 @@ TISInputSourceWrapper::InitKeyEvent(NSEv
         aKeyEvent.mKeyValue.Truncate();
       }
     }
   } else {
     // Compute the key for non-printable keys and some special printable keys.
     aKeyEvent.mKeyNameIndex = ComputeGeckoKeyNameIndex(nativeKeyCode);
   }
 
-  aKeyEvent.mCodeNameIndex = ComputeGeckoCodeNameIndex(nativeKeyCode);
+  aKeyEvent.mCodeNameIndex = ComputeGeckoCodeNameIndex(nativeKeyCode, kbType);
   MOZ_ASSERT(aKeyEvent.mCodeNameIndex != CODE_NAME_INDEX_USE_STRING);
 
   NS_OBJC_END_TRY_ABORT_BLOCK
 }
 
 void
 TISInputSourceWrapper::WillDispatchKeyboardEvent(
                          NSEvent* aNativeKeyEvent,
@@ -1412,18 +1412,31 @@ TISInputSourceWrapper::ComputeGeckoKeyNa
 
     default:
       return KEY_NAME_INDEX_Unidentified;
   }
 }
 
 // static
 CodeNameIndex
-TISInputSourceWrapper::ComputeGeckoCodeNameIndex(UInt32 aNativeKeyCode)
+TISInputSourceWrapper::ComputeGeckoCodeNameIndex(UInt32 aNativeKeyCode,
+                                                 UInt32 aKbType)
 {
+  // macOS swaps native key code between Backquote key and IntlBackslash key
+  // only when the keyboard type is ISO.  Let's treat the key code after
+  // swapping them here because Chromium does so only when computing .code
+  // value.
+  if (::KBGetLayoutType(aKbType) == kKeyboardISO) {
+    if (aNativeKeyCode == kVK_ISO_Section) {
+      aNativeKeyCode = kVK_ANSI_Grave;
+    } else if (aNativeKeyCode == kVK_ANSI_Grave) {
+      aNativeKeyCode = kVK_ISO_Section;
+    }
+  }
+
   switch (aNativeKeyCode) {
 
 #define NS_NATIVE_KEY_TO_DOM_CODE_NAME_INDEX(aNativeKey, aCodeNameIndex) \
     case aNativeKey: return aCodeNameIndex;
 
 #include "NativeKeyToDOMCodeName.h"
 
 #undef NS_NATIVE_KEY_TO_DOM_CODE_NAME_INDEX