diff --git a/spacy/_ml.py b/spacy/_ml.py
index b09e2ef95..132bd55a2 100644
--- a/spacy/_ml.py
+++ b/spacy/_ml.py
@@ -18,51 +18,8 @@ from .tokens.doc import Doc
 
 import numpy
 import io
-import msgpack
-import msgpack_numpy
-msgpack_numpy.patch()
 
 
-def model_to_bytes(model):
-    weights = []
-    metas = []
-    dims = []
-    queue = [model]
-    i = 0
-    for layer in queue:
-        if hasattr(layer, '_mem'):
-            weights.append(layer._mem.weights)
-            metas.append(tuple(layer._mem._offsets))
-            dims.append(getattr(layer, '_dims', None))
-            i += 1
-        if hasattr(layer, '_layers'):
-            queue.extend(layer._layers)
-    data = {'metas': tuple(metas), 'weights': tuple(weights), 'dims':
-            tuple(dims)}
-    return msgpack.dumps(data)
-
-
-def model_from_bytes(model, bytes_data):
-    data = msgpack.loads(bytes_data)
-    metas = data['metas']
-    weights = data['weights']
-    dims = data['dims']
-    queue = [model]
-    i = 0
-    for layer in queue:
-        if hasattr(layer, '_mem'):
-            params = weights[i]
-            flat_mem = layer._mem._mem.ravel()
-            flat_params = params.ravel()
-            flat_mem[:flat_params.size] = flat_params
-            layer._mem._offsets.update(metas[i])
-            if hasattr(layer, '_dims'):
-                layer._dims.update(dims[i])
-            i += 1
-        if hasattr(layer, '_layers'):
-            queue.extend(layer._layers)
- 
-
 def _init_for_precomputed(W, ops):
     if (W**2).sum() != 0.:
         return
diff --git a/spacy/tests/test_misc.py b/spacy/tests/test_misc.py
index 404422289..2c0ff0520 100644
--- a/spacy/tests/test_misc.py
+++ b/spacy/tests/test_misc.py
@@ -2,7 +2,7 @@
 from __future__ import unicode_literals
 
 from ..util import ensure_path
-from .._ml import model_to_bytes, model_from_bytes
+from ..util import model_to_bytes, model_from_bytes
 
 from pathlib import Path
 import pytest
diff --git a/spacy/util.py b/spacy/util.py
index 5766d2db1..72dede705 100644
--- a/spacy/util.py
+++ b/spacy/util.py
@@ -11,6 +11,10 @@ import sys
 import textwrap
 import random
 
+import msgpack
+import msgpack_numpy
+msgpack_numpy.patch()
+
 from .symbols import ORTH
 from .compat import cupy, CudaStream, path2str, basestring_, input_, unicode_
 
@@ -408,18 +412,62 @@ def get_raw_input(description, default=False):
     return user_input
 
 
-def to_bytes(unserialized, exclude):
+def to_bytes(getters, exclude):
     serialized = {}
-    for key, value in unserialized.items():
-        if key in exclude:
-            continue
-        elif hasattr(value, 'to_bytes'):
-            serialized[key] = value.to_bytes()
-        else:
-            serialized[key] = ujson.dumps(value)
-    return ujson.dumps(serialized)
+    for key, getter in getters.items():
+        if key not in exclude:
+            serialized[key] = getter()
+    return messagepack.dumps(serialized)
 
 
+def from_bytes(bytes_data, setters, exclude):
+    msg = messagepack.loads(bytes_data)
+    for key, setter in setters.items():
+        if key not in exclude:
+            setter(msg[key])
+    return msg
+
+
+def model_to_bytes(model):
+    weights = []
+    metas = []
+    dims = []
+    queue = [model]
+    i = 0
+    for layer in queue:
+        if hasattr(layer, '_mem'):
+            weights.append(layer._mem.weights)
+            metas.append(tuple(layer._mem._offsets))
+            dims.append(getattr(layer, '_dims', None))
+            i += 1
+        if hasattr(layer, '_layers'):
+            queue.extend(layer._layers)
+    data = {'metas': tuple(metas), 'weights': tuple(weights), 'dims':
+            tuple(dims)}
+    return msgpack.dumps(data)
+
+
+def model_from_bytes(model, bytes_data):
+    data = msgpack.loads(bytes_data)
+    metas = data['metas']
+    weights = data['weights']
+    dims = data['dims']
+    queue = [model]
+    i = 0
+    for layer in queue:
+        if hasattr(layer, '_mem'):
+            params = weights[i]
+            flat_mem = layer._mem._mem.ravel()
+            flat_params = params.ravel()
+            flat_mem[:flat_params.size] = flat_params
+            layer._mem._offsets.update(metas[i])
+            if hasattr(layer, '_dims'):
+                layer._dims.update(dims[i])
+            i += 1
+        if hasattr(layer, '_layers'):
+            queue.extend(layer._layers)
+ 
+
 def print_table(data, title=None):
     """Print data in table format.