Layer appears negative when gerbers are generated

[Mark]

I converted a design from PADS to Altium and generated the gerbers from the (modified) Altium design. 
I imported the PADS gerbers and Altium gerbers into CAMtastic files for comparison. 

It looks like one of the internal layers is now a negative:
(old PADS vs new Altium)



I've never seen this before, is it a problem with settings or will the PCB fabricator know it is negative?  (Yes, I did ask them, but no response to the question, just a quote). 

thanks. 

Edited to add: This is the only layer that shows up as a "plane".  Normally I would just use a poly pour but this is the way it imported.   

[ajb]

That's just how Altium exports plane layers.  Your only options AFAIK, are to leave the gerber negative and let your fabricator know, or to replace the plane layer with a signal layer and place a polygon.  Since plane layers are pretty straightforward, it should be fairly low risk to do the latter, as long as there aren't any complicated clearance/connection rules or voided areas.