Using built-in icons in Visual Studio extension

What step do I need to follow to use some of the built-in icons of Visual Studio in my extension toolbar (e.g. Open, Save, Run, Break icons)?

I have tried using constants such as cmdidSave from stdidcmd.h in my VSCT file like this:

<Button guid="guidBBTWindowPackageCmdSet" id="cmdidMyButton1" priority="0x0101" type="Button"><Parent guid="guidBBTWindowPackageCmdSet" id="ToolbarGroupID"/><Icon guid="CMDSETID_StandardCommandSet14" id="cmdidSave" /><Strings><CommandName>cmdidMyCommand1</CommandName><ButtonText>Load File</ButtonText></Strings></Button>

But it doesn't show the icon. Instead it starts showing the button in text style (text caption instead of image).

On the other hand, it works fine if I use the "image strip method" (as done in the default extension template), but that's not what I want to do.

This is VS2015 + .NET Framework 4.6 if that has anything to do.