Units do not seem to be parsed properly

[filmaj]

Version of package: 1.5.6
Node version: 10.9.0

➜ node
> parse=require('recipe-ingredient-parser').parse
[Function: parse]
> parse('- ½ cup coconut flour')
{ quantity: '0.5',
  unit: null,
  ingredient: '-  cup coconut flour' }
> parse('- 1 ½ teaspoon vanilla extract')
{ quantity: '1.5',
  unit: null,
  ingredient: '- 1  teaspoon vanilla extract' }

Expected behaviour: "cup" and "teaspoon" should be parsed as units.

Actual behaviour: unit seems to end up under ingredient, unit is null

[filmaj]

I was able to work around this by removing the leading slash - that seems to mess things up.