CLI bitmap export failure with 'maskContentUnits="objectBoundingBox"'

A mask which defines its content in objectBoundingBox units fails to get exported correctly to PNG via command line. Exporting the same content to PNG via GUI on the other hand produces the expected result.

Steps to reproduce:
1) open mask-cli-export-failure-1.svg in Inkscape
2) export via 'File > Export PNG Image' (page area)
3) quit inkscape
4) export via command line:
$ inkscape -f mask-cli-export-failure-1.svg -e mask-cli-export-failure-1-cli.png
5) compare the two exported PNG images

Expected result:
The two exported PNG images are identical

Actual result:
The PNG created via cli export appears to miss the masked object (probably the size of the mask content (a rectangle) was incorrectly calculated).

Reproduced on OS X 10.7.5 with
- Inkscape 0.47
- any version of the stable series 0.48.x
- current trunk (0.48+devel r13340)