diff --git a/CHANGES.rst b/CHANGES.rst
index 82605a21..46670446 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -1,6 +1,23 @@
 Change Log
 ----------
 
+1.1
+~~~
+
+UNRELEASED
+
+Breaking changes:
+
+* Drop support for Python 3.3. (#358)
+* Drop support for Python 3.4. (#421)
+
+Other changes:
+
+* Try to import from `collections.abc` to remove DeprecationWarning and ensure
+  `html5lib` keeps working in future Python versions. (#403)
+* Drop optional `datrie` dependency. (#442)
+
+
 1.0.1
 ~~~~~
 
diff --git a/README.rst b/README.rst
index fb9398f6..cec41d71 100644
--- a/README.rst
+++ b/README.rst
@@ -107,9 +107,6 @@ Optional Dependencies
 The following third-party libraries may be used for additional
 functionality:
 
-- ``datrie`` can be used under CPython to improve parsing performance
-  (though in almost all cases the improvement is marginal);
-
 - ``lxml`` is supported as a tree format (for both building and
   walking) under CPython (but *not* PyPy where it is known to cause
   segfaults);
diff --git a/debug-info.py b/debug-info.py
index f93fbdbe..b47b8ebf 100644
--- a/debug-info.py
+++ b/debug-info.py
@@ -12,7 +12,7 @@
     "maxsize": sys.maxsize
 }
 
-search_modules = ["chardet", "datrie", "genshi", "html5lib", "lxml", "six"]
+search_modules = ["chardet", "genshi", "html5lib", "lxml", "six"]
 found_modules = []
 
 for m in search_modules:
diff --git a/html5lib/_trie/__init__.py b/html5lib/_trie/__init__.py
index a5ba4bf1..07bad5d3 100644
--- a/html5lib/_trie/__init__.py
+++ b/html5lib/_trie/__init__.py
@@ -1,14 +1,5 @@
 from __future__ import absolute_import, division, unicode_literals
 
-from .py import Trie as PyTrie
+from .py import Trie
 
-Trie = PyTrie
-
-# pylint:disable=wrong-import-position
-try:
-    from .datrie import Trie as DATrie
-except ImportError:
-    pass
-else:
-    Trie = DATrie
-# pylint:enable=wrong-import-position
+__all__ = ["Trie"]
diff --git a/html5lib/_trie/datrie.py b/html5lib/_trie/datrie.py
deleted file mode 100644
index 51f3d046..00000000
--- a/html5lib/_trie/datrie.py
+++ /dev/null
@@ -1,44 +0,0 @@
-from __future__ import absolute_import, division, unicode_literals
-
-from datrie import Trie as DATrie
-from six import text_type
-
-from ._base import Trie as ABCTrie
-
-
-class Trie(ABCTrie):
-    def __init__(self, data):
-        chars = set()
-        for key in data.keys():
-            if not isinstance(key, text_type):
-                raise TypeError("All keys must be strings")
-            for char in key:
-                chars.add(char)
-
-        self._data = DATrie("".join(chars))
-        for key, value in data.items():
-            self._data[key] = value
-
-    def __contains__(self, key):
-        return key in self._data
-
-    def __len__(self):
-        return len(self._data)
-
-    def __iter__(self):
-        raise NotImplementedError()
-
-    def __getitem__(self, key):
-        return self._data[key]
-
-    def keys(self, prefix=None):
-        return self._data.keys(prefix)
-
-    def has_keys_with_prefix(self, prefix):
-        return self._data.has_keys_with_prefix(prefix)
-
-    def longest_prefix(self, prefix):
-        return self._data.longest_prefix(prefix)
-
-    def longest_prefix_item(self, prefix):
-        return self._data.longest_prefix_item(prefix)
diff --git a/requirements-optional.txt b/requirements-optional.txt
index d8be39ff..2e78c952 100644
--- a/requirements-optional.txt
+++ b/requirements-optional.txt
@@ -11,9 +11,3 @@ chardet>=2.2
 # lxml is supported with its own treebuilder ("lxml") and otherwise
 # uses the standard ElementTree support
 lxml ; platform_python_implementation == 'CPython'
-
-# DATrie can be used in place of our Python trie implementation for
-# slightly better parsing performance.
-# https://github.com/pytries/datrie/issues/52 although closed is not
-# yet released to https://pypi.org/project/datrie
-datrie ; platform_python_implementation == 'CPython' and python_version < '3.7'
diff --git a/setup.py b/setup.py
index d3841290..f84c1284 100644
--- a/setup.py
+++ b/setup.py
@@ -111,7 +111,6 @@ def default_environment():
       extras_require={
           # A conditional extra will only install these items when the extra is
           # requested and the condition matches.
-          "datrie:platform_python_implementation == 'CPython'": ["datrie"],
           "lxml:platform_python_implementation == 'CPython'": ["lxml"],
 
           # Standard extras, will be installed when the extra is requested.
@@ -123,6 +122,6 @@ def default_environment():
           # extra that will be installed whenever the condition matches and the
           # all extra is requested.
           "all": ["genshi", "chardet>=2.2"],
-          "all:platform_python_implementation == 'CPython'": ["datrie", "lxml"],
+          "all:platform_python_implementation == 'CPython'": ["lxml"],
       },
       )