diff --git a/CHANGES b/CHANGES
index f7003992e..20d3f5269 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,6 +1,8 @@
 Release 0.5.1 (in development)
 ==============================
 
+* Fix autodoc crash when automethod is used outside a class context.
+
 * Fix LaTeX writer output for images with specified height.
 
 * Fix wrong generated image path when including images in sources
diff --git a/sphinx/ext/autodoc.py b/sphinx/ext/autodoc.py
index bb7af93c6..ddaba04cc 100644
--- a/sphinx/ext/autodoc.py
+++ b/sphinx/ext/autodoc.py
@@ -321,6 +321,9 @@ class RstGenerator(object):
                 # ... or from a class directive
                 if mod_cls is None:
                     mod_cls = self.env.currclass
+                # ... if still None, there's no way to know
+                if mod_cls is None:
+                    return fullname, None, [], args, retann
             mod, cls = rpartition(mod_cls, '.')
             # if the module name is still missing, get it like above
             if not mod and hasattr(self.env, 'autodoc_current_module'):