I'm using the commandline tool to export to Unity. But I can't seem to get premultiplied alpha disabled so in Unity I get warnings "Warning: Premultiply-alpha atlas textures not supported in Linear color space!".

But I don't know what I'm doing wrong, I have an spine-export.json that I've validated is being used. Here it is in all it's glory:

{
"class": "export-binary",
"extension": ".skel.bytes",
"nonessential": true,
"cleanUp": true,
"packAtlas": {
   "stripWhitespaceX": true,
   "stripWhitespaceY": true,
   "rotation": true,
   "alias": true,
   "ignoreBlankImages": false,
   "alphaThreshold": 3,
   "minWidth": 16,
   "minHeight": 16,
   "maxWidth": 2048,
   "maxHeight": 2048,
   "pot": false,
   "multipleOfFour": false,
   "square": false,
   "outputFormat": "png",
   "jpegQuality": 0.9,
   "premultiplyAlpha": false,
   "bleed": false,
   "scale": [ 0.5 ],
   "scaleSuffix": [ "" ],
   "scaleResampling": [ "auto" ],
   "paddingX": 2,
   "paddingY": 2,
   "edgePadding": true,
   "duplicatePadding": false,
   "filterMin": "Linear",
   "filterMag": "Linear",
   "wrapX": "ClampToEdge",
   "wrapY": "ClampToEdge",
   "format": "RGBA8888",
   "atlasExtension": ".atlas.txt",
   "combineSubdirectories": false,
   "flattenPaths": false,
   "useIndexes": false,
   "debug": false,
   "fast": false,
   "limitMemory": true,
   "currentProject": true,
   "packing": "rectangles",
   "prettyPrint": false,
   "legacyOutput": false,
   "bleedIterations": 2,
   "ignore": false,
   "separator": "_",
   "silent": false
},
"warnings": true,
"open": false
}

So there within packAtlas premultipliedAlpha is set to false.

What could I be doing wrong? Thanks!