diff --git a/ChangeLog b/ChangeLog
new file mode 100644
index 0000000..ba4c69b
--- /dev/null
+++ b/ChangeLog
@@ -0,0 +1 @@
+.. This is a generated file! Do not edit.
diff --git a/automaton/_utils.py b/automaton/_utils.py
index 471701e..49feb02 100644
--- a/automaton/_utils.py
+++ b/automaton/_utils.py
@@ -42,7 +42,9 @@ def get_callback_name(cb):
         return repr(cb)
     else:
         try:
-            segments.insert(0, cb.__module__)
+            # When running under sphinx it appears this can be none?
+            if cb.__module__:
+                segments.insert(0, cb.__module__)
         except AttributeError:
             pass
         return ".".join(segments)
diff --git a/doc/source/examples.rst b/doc/source/examples.rst
index 736ac97..25f4538 100644
--- a/doc/source/examples.rst
+++ b/doc/source/examples.rst
@@ -42,6 +42,7 @@ Transitioning a simple machine
     m.process_event('fall')
     print(m.pformat())
     print(m.current_state)
+    print(m.terminated)
 
 **Expected output:**
 
diff --git a/test-requirements.txt b/test-requirements.txt
index 3e77e7a..14c39c2 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -4,6 +4,7 @@
 
 hacking<0.11,>=0.10.0
 
+doc8 # Apache-2.0
 coverage>=3.6
 discover
 python-subunit>=0.0.18
diff --git a/tox.ini b/tox.ini
index cd87575..47e4134 100644
--- a/tox.ini
+++ b/tox.ini
@@ -21,6 +21,12 @@ commands = python setup.py test --slowest --testr-args='{posargs}'
 [testenv:pep8]
 commands = flake8 {posargs}
 
+[testenv:py27]
+commands =
+    python setup.py testr --slowest --testr-args='{posargs}'
+    sphinx-build -b doctest doc/source doc/build
+    doc8 doc/source
+
 [testenv:venv]
 basepython = python2.7
 commands = {posargs}