Broken icon on large installer?

I am in the process of creating a huge installer exe (about 900 megabytes) and every time I compile, the icon on the installer is broken and defaults to the standard "unknown EXE" icon. This is weird because I have

!define INSTALL_ICON			"${NSISDIR}\Contrib\Graphics\Icons\win-install.ico"

[...]

!define MUI_ICON "${INSTALL_ICON}"

Which has worked perfectly fine on every other installer I've made (quite a few), but all of which were much smaller than 900 megs. So all I can think is that the large filesize is somehow causing NSIS to screw up and not create the icon correctly.

I suppose I could try using another program to set the icon, but that will change the file's checksum and presumably cause the installer to exit with an error message.

This is standard Windows behavior. Icons for large files are not displayed to speed up displaying the contents of a folder.

Really? Because I feel like I've downloaded large EXEs that had working icons before. What is the size limit before Windows gives up and doesn't look for an icon?

Stu