SharePoint field set to not required but still requires input

This field is part of a custom list definition in a feature. Originally this was a required field. The change to not being required was done simply by removing the "Required='TRUE'" from the schema.xml, packaged as a solution, deployed via stsadm -o upgradesolution, etc.

It works a开发者_开发百科s it should on my dev box but not on staging. I've compared the field element xml strings and they are identical (via SP Manager 2007).

I've tried setting it to required and back again via the UI, no change.

Any ideas?

Is this field used in a Content Type? If yes, then you might have to remove the Required='TRUE' from the Content Type section of the schema as well. Or if this field or its content type is declared at the web level, make sure you change the required attribute at that level as well.