Placed Graphic non-CMYK compatible error

[adcworks]

Hi

I have created a logo in Illustrator and saved it as a CMYK EPS. The logo is completely white, nothing else, so CMYK values are all 0.

I start a new document in InDesign and place this logo in the middle.

Then I do File > Export and choose PDF/X1a compliant.

I get an error message

"Colour in one or more placed graphics cannot be reproduced as CMYK for PDF/X1a document"

This seems odd to me given that the logo is only white, is definately from a CMYK document and is an EPS.

Any tips on someting I could be missing?

Thanks!