diff --git a/js/src/xpconnect/shell/xpcshell.cpp b/js/src/xpconnect/shell/xpcshell.cpp
index 00834fbf5dc0..b061ad207d8e 100644
--- a/js/src/xpconnect/shell/xpcshell.cpp
+++ b/js/src/xpconnect/shell/xpcshell.cpp
@@ -1,4 +1,4 @@
-/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
  *
  * The contents of this file are subject to the Netscape Public License
  * Version 1.0 (the "NPL"); you may not use this file except in
diff --git a/js/src/xpconnect/src/nsXPConnect.cpp b/js/src/xpconnect/src/nsXPConnect.cpp
index c3faf03bfbc6..340361748873 100644
--- a/js/src/xpconnect/src/nsXPConnect.cpp
+++ b/js/src/xpconnect/src/nsXPConnect.cpp
@@ -1,4 +1,4 @@
-/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
  *
  * The contents of this file are subject to the Netscape Public License
  * Version 1.0 (the "NPL"); you may not use this file except in
diff --git a/js/src/xpconnect/src/xpcarbitrary.cpp b/js/src/xpconnect/src/xpcarbitrary.cpp
index d175dbd73b7f..1367be9641c1 100644
--- a/js/src/xpconnect/src/xpcarbitrary.cpp
+++ b/js/src/xpconnect/src/xpcarbitrary.cpp
@@ -1,4 +1,4 @@
-/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
  *
  * The contents of this file are subject to the Netscape Public License
  * Version 1.0 (the "NPL"); you may not use this file except in
diff --git a/js/src/xpconnect/src/xpccomponents.cpp b/js/src/xpconnect/src/xpccomponents.cpp
index 85097037b45d..0007e8d83c21 100644
--- a/js/src/xpconnect/src/xpccomponents.cpp
+++ b/js/src/xpconnect/src/xpccomponents.cpp
@@ -1,4 +1,4 @@
-/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
  *
  * The contents of this file are subject to the Netscape Public License
  * Version 1.0 (the "NPL"); you may not use this file except in
diff --git a/js/src/xpconnect/src/xpccontext.cpp b/js/src/xpconnect/src/xpccontext.cpp
index 897bebcb065c..b7675b9830a0 100644
--- a/js/src/xpconnect/src/xpccontext.cpp
+++ b/js/src/xpconnect/src/xpccontext.cpp
@@ -1,4 +1,4 @@
-/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
  *
  * The contents of this file are subject to the Netscape Public License
  * Version 1.0 (the "NPL"); you may not use this file except in
diff --git a/js/src/xpconnect/src/xpcconvert.cpp b/js/src/xpconnect/src/xpcconvert.cpp
index 592b620ba918..af778e143227 100644
--- a/js/src/xpconnect/src/xpcconvert.cpp
+++ b/js/src/xpconnect/src/xpcconvert.cpp
@@ -1,4 +1,4 @@
-/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
  *
  * The contents of this file are subject to the Netscape Public License
  * Version 1.0 (the "NPL"); you may not use this file except in
diff --git a/js/src/xpconnect/src/xpcjsid.cpp b/js/src/xpconnect/src/xpcjsid.cpp
index 6c87aad2c743..0cc6fb40e478 100644
--- a/js/src/xpconnect/src/xpcjsid.cpp
+++ b/js/src/xpconnect/src/xpcjsid.cpp
@@ -1,4 +1,4 @@
-/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
  *
  * The contents of this file are subject to the Netscape Public License
  * Version 1.0 (the "NPL"); you may not use this file except in
diff --git a/js/src/xpconnect/src/xpclog.cpp b/js/src/xpconnect/src/xpclog.cpp
index 100cc927a8c4..a0c01fe892ba 100644
--- a/js/src/xpconnect/src/xpclog.cpp
+++ b/js/src/xpconnect/src/xpclog.cpp
@@ -1,4 +1,4 @@
-/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
  *
  * The contents of this file are subject to the Netscape Public License
  * Version 1.0 (the "NPL"); you may not use this file except in
diff --git a/js/src/xpconnect/src/xpcmaps.cpp b/js/src/xpconnect/src/xpcmaps.cpp
index 6cb8002871d5..8142f892b706 100644
--- a/js/src/xpconnect/src/xpcmaps.cpp
+++ b/js/src/xpconnect/src/xpcmaps.cpp
@@ -1,4 +1,4 @@
-/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
  *
  * The contents of this file are subject to the Netscape Public License
  * Version 1.0 (the "NPL"); you may not use this file except in
diff --git a/js/src/xpconnect/src/xpcmodule.cpp b/js/src/xpconnect/src/xpcmodule.cpp
index 49a422f2571c..04bb29643aaa 100644
--- a/js/src/xpconnect/src/xpcmodule.cpp
+++ b/js/src/xpconnect/src/xpcmodule.cpp
@@ -1,4 +1,4 @@
-/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
  *
  * The contents of this file are subject to the Netscape Public License
  * Version 1.0 (the "NPL"); you may not use this file except in
diff --git a/js/src/xpconnect/src/xpcthrower.cpp b/js/src/xpconnect/src/xpcthrower.cpp
index c95cea884f6e..45fcc71e9627 100644
--- a/js/src/xpconnect/src/xpcthrower.cpp
+++ b/js/src/xpconnect/src/xpcthrower.cpp
@@ -1,4 +1,4 @@
-/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
  *
  * The contents of this file are subject to the Netscape Public License
  * Version 1.0 (the "NPL"); you may not use this file except in
diff --git a/js/src/xpconnect/src/xpcwrappedjs.cpp b/js/src/xpconnect/src/xpcwrappedjs.cpp
index 659a83f8d3e1..36b86792297d 100644
--- a/js/src/xpconnect/src/xpcwrappedjs.cpp
+++ b/js/src/xpconnect/src/xpcwrappedjs.cpp
@@ -1,4 +1,4 @@
-/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
  *
  * The contents of this file are subject to the Netscape Public License
  * Version 1.0 (the "NPL"); you may not use this file except in
diff --git a/js/src/xpconnect/src/xpcwrappedjsclass.cpp b/js/src/xpconnect/src/xpcwrappedjsclass.cpp
index b80e2e6701d5..bec51b45c83c 100644
--- a/js/src/xpconnect/src/xpcwrappedjsclass.cpp
+++ b/js/src/xpconnect/src/xpcwrappedjsclass.cpp
@@ -1,4 +1,4 @@
-/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
  *
  * The contents of this file are subject to the Netscape Public License
  * Version 1.0 (the "NPL"); you may not use this file except in
diff --git a/js/src/xpconnect/src/xpcwrappednative.cpp b/js/src/xpconnect/src/xpcwrappednative.cpp
index b87ce5f7dc25..8dfb13ca907e 100644
--- a/js/src/xpconnect/src/xpcwrappednative.cpp
+++ b/js/src/xpconnect/src/xpcwrappednative.cpp
@@ -1,4 +1,4 @@
-/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
  *
  * The contents of this file are subject to the Netscape Public License
  * Version 1.0 (the "NPL"); you may not use this file except in
diff --git a/js/src/xpconnect/src/xpcwrappednativeclass.cpp b/js/src/xpconnect/src/xpcwrappednativeclass.cpp
index 0ce0b95d2d61..fd9d896cfefa 100644
--- a/js/src/xpconnect/src/xpcwrappednativeclass.cpp
+++ b/js/src/xpconnect/src/xpcwrappednativeclass.cpp
@@ -1,4 +1,4 @@
-/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
  *
  * The contents of this file are subject to the Netscape Public License
  * Version 1.0 (the "NPL"); you may not use this file except in
diff --git a/js/src/xpconnect/tests/TestXPC.cpp b/js/src/xpconnect/tests/TestXPC.cpp
index fe105c26e7cc..4dbf5a02ca8a 100644
--- a/js/src/xpconnect/tests/TestXPC.cpp
+++ b/js/src/xpconnect/tests/TestXPC.cpp
@@ -1,4 +1,4 @@
-/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
  *
  * The contents of this file are subject to the Netscape Public License
  * Version 1.0 (the "NPL"); you may not use this file except in
diff --git a/js/src/xpconnect/tests/xpctest_echo.js b/js/src/xpconnect/tests/xpctest_echo.js
index 097f4ce01164..2168da311704 100644
--- a/js/src/xpconnect/tests/xpctest_echo.js
+++ b/js/src/xpconnect/tests/xpctest_echo.js
@@ -1,4 +1,4 @@
-/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
  *
  * The contents of this file are subject to the Netscape Public License
  * Version 1.0 (the "NPL"); you may not use this file except in