diff --git a/data/lm/generate_package.py b/data/lm/generate_package.py
deleted file mode 100644
index 30a33fcc..00000000
--- a/data/lm/generate_package.py
+++ /dev/null
@@ -1,157 +0,0 @@
-#!/usr/bin/env python
-from __future__ import absolute_import, division, print_function
-
-import argparse
-import shutil
-import sys
-
-import ds_ctcdecoder
-from deepspeech_training.util.text import Alphabet, UTF8Alphabet
-from ds_ctcdecoder import Scorer, Alphabet as NativeAlphabet
-
-
-def create_bundle(
-    alphabet_path,
-    lm_path,
-    vocab_path,
-    package_path,
-    force_utf8,
-    default_alpha,
-    default_beta,
-):
-    words = set()
-    vocab_looks_char_based = True
-    with open(vocab_path) as fin:
-        for line in fin:
-            for word in line.split():
-                words.add(word.encode("utf-8"))
-                if len(word) > 1:
-                    vocab_looks_char_based = False
-    print("{} unique words read from vocabulary file.".format(len(words)))
-
-    cbm = "Looks" if vocab_looks_char_based else "Doesn't look"
-    print("{} like a character based model.".format(cbm))
-
-    if force_utf8 != None:  # pylint: disable=singleton-comparison
-        use_utf8 = force_utf8.value
-    else:
-        use_utf8 = vocab_looks_char_based
-        print("Using detected UTF-8 mode: {}".format(use_utf8))
-
-    if use_utf8:
-        serialized_alphabet = UTF8Alphabet().serialize()
-    else:
-        if not alphabet_path:
-            raise RuntimeError("No --alphabet path specified, can't continue.")
-        serialized_alphabet = Alphabet(alphabet_path).serialize()
-
-    alphabet = NativeAlphabet()
-    err = alphabet.deserialize(serialized_alphabet, len(serialized_alphabet))
-    if err != 0:
-        raise RuntimeError("Error loading alphabet: {}".format(err))
-
-    scorer = Scorer()
-    scorer.set_alphabet(alphabet)
-    scorer.set_utf8_mode(use_utf8)
-    scorer.reset_params(default_alpha, default_beta)
-    err = scorer.load_lm(lm_path)
-    if err != ds_ctcdecoder.DS_ERR_SCORER_NO_TRIE:
-        print('Error loading language model file: 0x{:X}.'.format(err))
-        print('See the error codes section in https://deepspeech.readthedocs.io for a description.')
-        sys.exit(1)
-    scorer.fill_dictionary(list(words))
-    shutil.copy(lm_path, package_path)
-    # append, not overwrite
-    if scorer.save_dictionary(package_path, True):
-        print("Package created in {}".format(package_path))
-    else:
-        print("Error when creating {}".format(package_path))
-        sys.exit(1)
-
-
-class Tristate(object):
-    def __init__(self, value=None):
-        if any(value is v for v in (True, False, None)):
-            self.value = value
-        else:
-            raise ValueError("Tristate value must be True, False, or None")
-
-    def __eq__(self, other):
-        return (
-            self.value is other.value
-            if isinstance(other, Tristate)
-            else self.value is other
-        )
-
-    def __ne__(self, other):
-        return not self == other
-
-    def __bool__(self):
-        raise TypeError("Tristate object may not be used as a Boolean")
-
-    def __str__(self):
-        return str(self.value)
-
-    def __repr__(self):
-        return "Tristate(%s)" % self.value
-
-
-def main():
-    parser = argparse.ArgumentParser(
-        description="Generate an external scorer package for DeepSpeech."
-    )
-    parser.add_argument(
-        "--alphabet",
-        help="Path of alphabet file to use for vocabulary construction. Words with characters not in the alphabet will not be included in the vocabulary. Optional if using UTF-8 mode.",
-    )
-    parser.add_argument(
-        "--lm",
-        required=True,
-        help="Path of KenLM binary LM file. Must be built without including the vocabulary (use the -v flag). See generate_lm.py for how to create a binary LM.",
-    )
-    parser.add_argument(
-        "--vocab",
-        required=True,
-        help="Path of vocabulary file. Must contain words separated by whitespace.",
-    )
-    parser.add_argument("--package", required=True, help="Path to save scorer package.")
-    parser.add_argument(
-        "--default_alpha",
-        type=float,
-        required=True,
-        help="Default value of alpha hyperparameter.",
-    )
-    parser.add_argument(
-        "--default_beta",
-        type=float,
-        required=True,
-        help="Default value of beta hyperparameter.",
-    )
-    parser.add_argument(
-        "--force_utf8",
-        type=str,
-        default="",
-        help="Boolean flag, force set or unset UTF-8 mode in the scorer package. If not set, infers from the vocabulary. See <https://github.com/mozilla/DeepSpeech/blob/master/doc/Decoder.rst#utf-8-mode> for further explanation",
-    )
-    args = parser.parse_args()
-
-    if args.force_utf8 in ("True", "1", "true", "yes", "y"):
-        force_utf8 = Tristate(True)
-    elif args.force_utf8 in ("False", "0", "false", "no", "n"):
-        force_utf8 = Tristate(False)
-    else:
-        force_utf8 = Tristate(None)
-
-    create_bundle(
-        args.alphabet,
-        args.lm,
-        args.vocab,
-        args.package,
-        force_utf8,
-        args.default_alpha,
-        args.default_beta,
-    )
-
-
-if __name__ == "__main__":
-    main()
diff --git a/native_client/BUILD b/native_client/BUILD
index 965a766c..36702088 100644
--- a/native_client/BUILD
+++ b/native_client/BUILD
@@ -2,6 +2,7 @@
 
 load("@org_tensorflow//tensorflow:tensorflow.bzl", "tf_cc_shared_object")
 load("@local_config_cuda//cuda:build_defs.bzl", "if_cuda")
+load("@com_github_nelhage_rules_boost//:boost/boost.bzl", "boost_deps")
 
 load(
     "@org_tensorflow//tensorflow/lite:build_def.bzl",
@@ -78,6 +79,8 @@ cc_library(
     hdrs = [
         "ctcdecode/ctc_beam_search_decoder.h",
         "ctcdecode/scorer.h",
+        "ctcdecode/decoder_utils.h",
+        "alphabet.h",
     ],
     includes = [
         ".",
@@ -186,6 +189,22 @@ genrule(
     cmd = "dsymutil $(location :libdeepspeech.so) -o $@"
 )
 
+cc_binary(
+    name = "generate_scorer_package",
+    srcs = [
+        "generate_scorer_package.cpp",
+        "deepspeech_errors.cc",
+    ],
+    copts = ["-std=c++11"],
+    deps = [
+        ":decoder",
+        "@com_google_absl//absl/flags:flag",
+        "@com_google_absl//absl/flags:parse",
+        "@com_google_absl//absl/types:optional",
+        "@boost//:program_options",
+    ],
+)
+
 cc_binary(
     name = "enumerate_kenlm_vocabulary",
     srcs = [
diff --git a/native_client/alphabet.h b/native_client/alphabet.h
index ace905cc..e57ef914 100644
--- a/native_client/alphabet.h
+++ b/native_client/alphabet.h
@@ -19,7 +19,7 @@ public:
   Alphabet(const Alphabet&) = default;
   Alphabet& operator=(const Alphabet&) = default;
 
-  int init(const char *config_file) {
+  virtual int init(const char *config_file) {
     std::ifstream in(config_file, std::ios::in);
     if (!in) {
       return 1;
@@ -45,6 +45,30 @@ public:
     return 0;
   }
 
+  std::string serialize() {
+    // Serialization format is a sequence of (key, value) pairs, where key is
+    // a uint16_t and value is a uint16_t length followed by `length` UTF-8
+    // encoded bytes with the label.
+    std::stringstream out;
+
+    // We start by writing the number of pairs in the buffer as uint16_t.
+    uint16_t size = size_;
+    out.write(reinterpret_cast<char*>(&size), sizeof(size));
+
+    for (auto it = label_to_str_.begin(); it != label_to_str_.end(); ++it) {
+      uint16_t key = it->first;
+      string str = it->second;
+      uint16_t len = str.length();
+      // Then we write the key as uint16_t, followed by the length of the value
+      // as uint16_t, followed by `length` bytes (the value itself).
+      out.write(reinterpret_cast<char*>(&key), sizeof(key));
+      out.write(reinterpret_cast<char*>(&len), sizeof(len));
+      out.write(str.data(), len);
+    }
+
+    return out.str();
+  }
+
   int deserialize(const char* buffer, const int buffer_size) {
     // See util/text.py for an explanation of the serialization format.
     int offset = 0;
@@ -126,11 +150,28 @@ public:
     return word;
   }
 
-private:
+protected:
   size_t size_;
   unsigned int space_label_;
   std::unordered_map<unsigned int, std::string> label_to_str_;
   std::unordered_map<std::string, unsigned int> str_to_label_;
 };
 
+class UTF8Alphabet : public Alphabet
+{
+public:
+  UTF8Alphabet() {
+    size_ = 255;
+    space_label_ = ' ' - 1;
+    for (int i = 0; i < size_; ++i) {
+      std::string val(1, i+1);
+      label_to_str_[i] = val;
+      str_to_label_[val] = i;
+    }
+  }
+
+  int init(const char*) override {}
+};
+
+
 #endif //ALPHABET_H
diff --git a/native_client/ctcdecode/scorer.cpp b/native_client/ctcdecode/scorer.cpp
index ebf55227..401613d1 100644
--- a/native_client/ctcdecode/scorer.cpp
+++ b/native_client/ctcdecode/scorer.cpp
@@ -357,7 +357,7 @@ std::vector<std::string> Scorer::make_ngram(PathTrie* prefix)
   return ngram;
 }
 
-void Scorer::fill_dictionary(const std::vector<std::string>& vocabulary)
+void Scorer::fill_dictionary(const std::unordered_set<std::string>& vocabulary)
 {
   // ConstFst is immutable, so we need to use a MutableFst to create the trie,
   // and then we convert to a ConstFst for the decoder and for storing on disk.
diff --git a/native_client/ctcdecode/scorer.h b/native_client/ctcdecode/scorer.h
index d2a1c8b3..3e7c0761 100644
--- a/native_client/ctcdecode/scorer.h
+++ b/native_client/ctcdecode/scorer.h
@@ -4,6 +4,7 @@
 #include <memory>
 #include <string>
 #include <unordered_map>
+#include <unordered_set>
 #include <vector>
 
 #include "lm/virtual_interface.hh"
@@ -83,7 +84,7 @@ public:
   bool is_scoring_boundary(PathTrie* prefix, size_t new_label);
 
   // fill dictionary FST from a vocabulary
-  void fill_dictionary(const std::vector<std::string> &vocabulary);
+  void fill_dictionary(const std::unordered_set<std::string> &vocabulary);
 
   // load language model from given path
   int load_lm(const std::string &lm_path);
diff --git a/native_client/generate_scorer_package.cpp b/native_client/generate_scorer_package.cpp
new file mode 100644
index 00000000..910bf9c2
--- /dev/null
+++ b/native_client/generate_scorer_package.cpp
@@ -0,0 +1,146 @@
+#include <string>
+#include <vector>
+#include <fstream>
+#include <unordered_set>
+#include <iostream>
+using namespace std;
+
+#include "absl/types/optional.h"
+#include "boost/program_options.hpp"
+
+#include "ctcdecode/decoder_utils.h"
+#include "ctcdecode/scorer.h"
+#include "alphabet.h"
+#include "deepspeech.h"
+
+namespace po = boost::program_options;
+
+int
+create_package(absl::optional<string> alphabet_path,
+               string lm_path,
+               string vocab_path,
+               string package_path,
+               absl::optional<bool> force_utf8,
+               float default_alpha,
+               float default_beta)
+{
+    // Read vocabulary
+    unordered_set<string> words;
+    bool vocab_looks_char_based = true;
+    ifstream fin(vocab_path);
+    if (!fin) {
+        cerr << "Invalid vocabulary file " << vocab_path << "\n";
+        return 1;
+    }
+    string word;
+    while (fin >> word) {
+        words.insert(word);
+        if (get_utf8_str_len(word) > 1) {
+            vocab_looks_char_based = false;
+        }
+    }
+    cerr << words.size() << " unique words read from vocabulary file.\n"
+         << (vocab_looks_char_based ? "Looks" : "Doesn't look")
+         << " like a character based (Bytes Are All You Need) model.\n";
+
+    if (!force_utf8.has_value()) {
+        force_utf8 = vocab_looks_char_based;
+        cerr << "--force_utf8 was not specified, using value "
+             << "infered from vocabulary contents: "
+             << (vocab_looks_char_based ? "true" : "false") << "\n";
+    }
+
+    if (force_utf8.value() && !alphabet_path.has_value()) {
+        cerr << "No --alphabet file specified, not using bytes output mode, can't continue.\n";
+        return 1;
+    }
+
+    Scorer scorer;
+    if (force_utf8.value()) {
+        scorer.set_alphabet(UTF8Alphabet());
+    } else {
+        Alphabet alphabet;
+        alphabet.init(alphabet_path->c_str());
+        scorer.set_alphabet(alphabet);
+    }
+    scorer.set_utf8_mode(force_utf8.value());
+    scorer.reset_params(default_alpha, default_beta);
+    int err = scorer.load_lm(lm_path);
+    if (err != DS_ERR_SCORER_NO_TRIE) {
+        cerr << "Error loading language model file: "
+             << DS_ErrorCodeToErrorMessage(err) << "\n";
+        return 1;
+    }
+    scorer.fill_dictionary(words);
+
+    // Copy LM file to final package file destination
+    {
+        ifstream lm_src(lm_path, std::ios::binary);
+        ofstream package_dest(package_path, std::ios::binary);
+        package_dest << lm_src.rdbuf();
+    }
+
+    // Save dictionary to package file, appending instead of overwriting
+    if (!scorer.save_dictionary(package_path, true)) {
+        cerr << "Error when saving package in " << package_path << ".\n";
+        return 1;
+    }
+
+    cerr << "Package created in " << package_path << ".\n";
+    return 0;
+}
+
+int
+main(int argc, char** argv)
+{
+    po::options_description desc("Options");
+    desc.add_options()
+        ("help", "show help message")
+        ("alphabet", po::value<string>(), "Path of alphabet file to use for vocabulary construction. Words with characters not in the alphabet will not be included in the vocabulary. Optional if using UTF-8 mode.")
+        ("lm", po::value<string>(), "Path of KenLM binary LM file. Must be built without including the vocabulary (use the -v flag). See generate_lm.py for how to create a binary LM.")
+        ("vocab", po::value<string>(), "Path of vocabulary file. Must contain words separated by whitespace.")
+        ("package", po::value<string>(), "Path to save scorer package.")
+        ("default_alpha", po::value<float>(), "Default value of alpha hyperparameter (float).")
+        ("default_beta", po::value<float>(), "Default value of beta hyperparameter (float).")
+        ("force_utf8", po::value<bool>(), "Boolean flag, force set or unset UTF-8 mode in the scorer package. If not set, infers from the vocabulary. See <https://deepspeech.readthedocs.io/en/master/Decoder.html#utf-8-mode> for further explanation.")
+    ;
+
+    po::variables_map vm;
+    po::store(po::parse_command_line(argc, argv, desc), vm);
+    po::notify(vm);
+
+    if (vm.count("help")) {
+        cout << desc << "\n";
+        return 1;
+    }
+
+    // Check required flags.
+    for (const string& flag : {"lm", "vocab", "package", "default_alpha", "default_beta"}) {
+        if (!vm.count(flag)) {
+            cerr << "--" << flag << " is a required flag. Pass --help for help.\n";
+            return 1;
+        }
+    }
+
+    // Parse optional --force_utf8
+    absl::optional<bool> force_utf8 = absl::nullopt;
+    if (vm.count("force_utf8")) {
+        force_utf8 = vm["force_utf8"].as<bool>();
+    }
+
+    // Parse optional --alphabet
+    absl::optional<string> alphabet = absl::nullopt;
+    if (vm.count("alphabet")) {
+        alphabet = vm["alphabet"].as<string>();
+    }
+
+    create_package(alphabet,
+                   vm["lm"].as<string>(),
+                   vm["vocab"].as<string>(),
+                   vm["package"].as<string>(),
+                   force_utf8,
+                   vm["default_alpha"].as<float>(),
+                   vm["default_beta"].as<float>());
+
+    return 0;
+}