         k = parseString()
       }
       if map[k] != nil && map[k].isValid {
-        return .Invalid("duplicate key \(k), \(context(buildContext()))")
+        return .Invalid("duplicate key \(k), \(buildContext())")
       }
       ignoreSpace()
       map = expect(.Colon, "expected colon", map)

      ignoreSpace()
      let k = parseString()
      if map[k] != nil && map[k].isValid {
        return .Invalid("duplicate key \(k), \(context(buildContext()))")
      }
      map[k] = nil
      map = expect(.Colon, "expected colon", map)

        break
      }
    }
    return context(text)
  }

  func ignoreSpace () {
