Cascading from the same server

[Howard Mark]

I'm attempting to create a single layer from a group of layers by cascading a WMS call from a server to itself. 
The WMS layer is defined in one map file and the layers it references are in another. 
An HTTP call to draw the second map (group of layers) works fine, but a call to the first map - using the WMS layer results in a "cannot draw layer" error.
Is this cascading not possible? Or should I look for typos...?

TIA for any info

Mark 




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