Error on parsing package.json {engine} symbol "<" (less than)

[jc3213]

nodejs 7.6.0(64bit) jpm 1.3.0 Win 10 64bit 14393

When I generate .xpi with package.json contains

  "engines": {
    "firefox": ">=38.0a1 <57.0"
  },

What I get in install.rdf is

            <Description>
              <em:id>{ec8030f7-c20a-464f-9b0e-13a3a9e97384}</em:id>
              <em:minVersion>38.0a1</em:minVersion>
              <em:maxVersion>57.0.-1</em:maxVersion>
</Description>

Which means the generated string should be 56.0 (57.0 - 1.0 or so).

Well, this does not affect much though