protobuf wrong enum encoding generation

test.proto

enum FOO {
  A = 1;
  B = 2;
}

message Message {
  optional bool bool_value = 1;
  optional float float_value = 2;
  optional int32 int_value = 3;
  optional string string_value = 4;
  optional FOO foo = 5;
}

test.proto.js

// This file is auto generated by the protocol-buffers cli tool

/* eslint-disable quotes */
/* eslint-disable indent */
/* eslint-disable no-redeclare */

// Remember to `npm install --save protocol-buffers-encodings`
var encodings = require('protocol-buffers-encodings')
var varint = encodings.varint
var skip = encodings.skip

var FOO = exports.FOO = {
  "A": 1,
  "B": 2
}

var Message = exports.Message = {
  buffer: true,
  encodingLength: null,
  encode: null,
  decode: null
}

defineMessage()

function defineMessage () {
  var enc = [
    encodings.bool,
    encodings.float,
    encodings.int32,
    encodings.string,
    undefined
  ]

  Message.encodingLength = encodingLength
  Message.encode = encode
  Message.decode = decode

  function encodingLength (obj) {
    var length = 0
    if (defined(obj.bool_value)) {
      var len = enc[0].encodingLength(obj.bool_value)
      length += 1 + len
    }
    if (defined(obj.float_value)) {
      var len = enc[1].encodingLength(obj.float_value)
      length += 1 + len
    }
    if (defined(obj.int_value)) {
      var len = enc[2].encodingLength(obj.int_value)
      length += 1 + len
    }
    if (defined(obj.string_value)) {
      var len = enc[3].encodingLength(obj.string_value)
      length += 1 + len
    }
    if (defined(obj.foo)) {
      var len = enc[4].encodingLength(obj.foo)
      length += 1 + len
    }
    return length
  }

  function encode (obj, buf, offset) {
    if (!offset) offset = 0
    if (!buf) buf = Buffer.allocUnsafe(encodingLength(obj))
    var oldOffset = offset
    if (defined(obj.bool_value)) {
      buf[offset++] = 8
      enc[0].encode(obj.bool_value, buf, offset)
      offset += enc[0].encode.bytes
    }
    if (defined(obj.float_value)) {
      buf[offset++] = 21
      enc[1].encode(obj.float_value, buf, offset)
      offset += enc[1].encode.bytes
    }
    if (defined(obj.int_value)) {
      buf[offset++] = 24
      enc[2].encode(obj.int_value, buf, offset)
      offset += enc[2].encode.bytes
    }
    if (defined(obj.string_value)) {
      buf[offset++] = 34
      enc[3].encode(obj.string_value, buf, offset)
      offset += enc[3].encode.bytes
    }
    if (defined(obj.foo)) {
      buf[offset++] = 40
      enc[4].encode(obj.foo, buf, offset)
      offset += enc[4].encode.bytes
    }
    encode.bytes = offset - oldOffset
    return buf
  }

  function decode (buf, offset, end) {
    if (!offset) offset = 0
    if (!end) end = buf.length
    if (!(end <= buf.length && offset <= buf.length)) throw new Error("Decoded message is not valid")
    var oldOffset = offset
    var obj = {
      bool_value: false,
      float_value: 0,
      int_value: 0,
      string_value: "",
      foo: 1
    }
    while (true) {
      if (end <= offset) {
        decode.bytes = offset - oldOffset
        return obj
      }
      var prefix = varint.decode(buf, offset)
      offset += varint.decode.bytes
      var tag = prefix >> 3
      switch (tag) {
        case 1:
        obj.bool_value = enc[0].decode(buf, offset)
        offset += enc[0].decode.bytes
        break
        case 2:
        obj.float_value = enc[1].decode(buf, offset)
        offset += enc[1].decode.bytes
        break
        case 3:
        obj.int_value = enc[2].decode(buf, offset)
        offset += enc[2].decode.bytes
        break
        case 4:
        obj.string_value = enc[3].decode(buf, offset)
        offset += enc[3].decode.bytes
        break
        case 5:
        obj.foo = enc[4].decode(buf, offset)
        offset += enc[4].decode.bytes
        break
        default:
        offset = skip(prefix & 7, buf, offset)
      }
    }
  }
}

function defined (val) {
  return val !== null && val !== undefined && (typeof val !== 'number' || !isNaN(val))
}