diff --git a/spacy/compat.py b/spacy/compat.py
index c2ab27d7e..4ef24cd8b 100644
--- a/spacy/compat.py
+++ b/spacy/compat.py
@@ -61,6 +61,14 @@ elif is_python3:
     json_dumps = lambda data: ujson.dumps(data, indent=2)
     path2str = lambda path: str(path)
 
+
+def b_to_str(b_str):
+    if is_python2:
+        return b_str
+    # important: if no encoding is set, string becomes "b'...'"
+    return str(b_str, encoding='utf8')
+
+
 def getattr_(obj, name, *default):
     if is_python3 and isinstance(name, bytes):
         name = name.decode('utf8')
diff --git a/spacy/displacy/__init__.py b/spacy/displacy/__init__.py
index 8468720cd..7c479f94c 100644
--- a/spacy/displacy/__init__.py
+++ b/spacy/displacy/__init__.py
@@ -3,6 +3,7 @@ from __future__ import unicode_literals
 
 from .render import DependencyRenderer, EntityRenderer
 from ..tokens import Doc
+from ..compat import b_to_str
 from ..util import prints, is_in_jupyter
 
 
@@ -65,7 +66,9 @@ def serve(docs, style='dep', page=True, minify=False, options={}, manual=False,
 
 
 def app(environ, start_response):
-    start_response('200 OK', [('Content-type', 'text/html; charset=utf-8')])
+    # headers and status need to be bytes in Python 2, see #1227
+    headers = [(b_to_str(b'Content-type'), b_to_str(b'text/html; charset=utf-8'))]
+    start_response(b_to_str(b'200 OK'), headers)
     res = _html['parsed'].encode(encoding='utf-8')
     return [res]
 
diff --git a/spacy/language.py b/spacy/language.py
index fad2e2119..0284c4636 100644
--- a/spacy/language.py
+++ b/spacy/language.py
@@ -292,6 +292,11 @@ class Language(object):
             >>>        for docs, golds in epoch:
             >>>            state = nlp.update(docs, golds, sgd=optimizer)
         """
+        if len(docs) != len(golds):
+            raise IndexError("Update expects same number of docs and golds "
+                "Got: %d, %d" % (len(docs), len(golds)))
+        if len(docs) == 0:
+            return
         tok2vec = self.pipeline[0]
         feats = tok2vec.doc2feats(docs)
         grads = {}
diff --git a/spacy/syntax/arc_eager.pyx b/spacy/syntax/arc_eager.pyx
index d4367c6df..29e8de0aa 100644
--- a/spacy/syntax/arc_eager.pyx
+++ b/spacy/syntax/arc_eager.pyx
@@ -362,7 +362,7 @@ cdef class ArcEager(TransitionSystem):
         if not self.has_gold(gold):
             return None
         for i in range(gold.length):
-            if gold.heads[i] is None: # Missing values
+            if gold.heads[i] is None or gold.labels[i] is None: # Missing values
                 gold.c.heads[i] = i
                 gold.c.has_dep[i] = False
             else: