minimum:0 should throw an error against minus values

[craftgear]

  var amanda = require('amanda')
  var person = {
    type: 'object',
    properties: {
      age: {
        type: 'number',
        minimum: 1,

      }
    }
  }
  amanda({age: -1},  person, function(error){
    console.log(error)
  })

this code should throw an error, but it doesn't.