BC5 conversion of PNG files swaps R and G channels

[c2aDS]

If I take an uncompressed normal map in BMP format and save it to PNG using photoshop or xnview for example (input images are the same at this step) and then use nvcompress to convert them both to DDS in BC5 format with these flags : nvcompress -bc5 myfile

The DDS from BMP file is correct when I open it in photoshop (even if the colors are washed out, the orientation is the same as in the uncompressed BMP image)
The DDS from PNG is incorrect : the red and green channels are swapped. The orientation is wrong in photoshop. If I swap the channels I get the right orientation (same result as BMP DDS)

[LMCrashy]

I've spotted this too, but when sampling the normal map everything seems to be ok.