diff --git a/src/core/api/qtwebenginecoreglobal.h b/src/core/api/qtwebenginecoreglobal.h
index 16daaab7d088a41d5619b8192d364dd94d281c7a..a17b355ebc693db86e664156eac3e613ac5bbf89 100644
--- a/src/core/api/qtwebenginecoreglobal.h
+++ b/src/core/api/qtwebenginecoreglobal.h
@@ -39,6 +39,8 @@
 
 #include <QtCore/qglobal.h>
 
+QT_BEGIN_NAMESPACE
+
 #if defined(BUILDING_CHROMIUM)
 #  define QWEBENGINE_EXPORT Q_DECL_EXPORT
 #else
@@ -47,4 +49,6 @@
 
 #define ASSERT_ENUMS_MATCH(A, B) Q_STATIC_ASSERT_X(static_cast<int>(A) == static_cast<int>(B), "The enum values must match");
 
+QT_END_NAMESPACE
+
 #endif // QTWEBENGINECOREGLOBAL_H
diff --git a/src/core/api/qwebenginecallback_p.h b/src/core/api/qwebenginecallback_p.h
index 9bc9b972734ed3184cd4c0c62a2f762112a858f4..348fed4647cd1701214b763b7bde1f4e85554f12 100644
--- a/src/core/api/qwebenginecallback_p.h
+++ b/src/core/api/qwebenginecallback_p.h
@@ -37,6 +37,17 @@
 #ifndef QWEBENGINECALLBACK_P_H
 #define QWEBENGINECALLBACK_P_H
 
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API.  It exists purely as an
+// implementation detail.  This header file may change from version to
+// version without notice, or even be removed.
+//
+// We mean it.
+//
+
 #include "qtwebenginecoreglobal_p.h"
 #include "qwebenginecallback.h"
 
diff --git a/src/core/api/qwebengineurlrequestinfo_p.h b/src/core/api/qwebengineurlrequestinfo_p.h
index df5f18d6e9aa24941cfe9d1400f3f6596d301f18..c78a93613089e6db266c78019a128d8c1e0d8555 100644
--- a/src/core/api/qwebengineurlrequestinfo_p.h
+++ b/src/core/api/qwebengineurlrequestinfo_p.h
@@ -37,6 +37,17 @@
 #ifndef QWEBENGINEURLREQUESTINFO_P_H
 #define QWEBENGINEURLREQUESTINFO_P_H
 
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API.  It exists purely as an
+// implementation detail.  This header file may change from version to
+// version without notice, or even be removed.
+//
+// We mean it.
+//
+
 #include "qtwebenginecoreglobal_p.h"
 
 #include "qwebengineurlrequestinfo.h"