diff --git a/sphinx/util/inspect.py b/sphinx/util/inspect.py
index 61061a9af..863e731ff 100644
--- a/sphinx/util/inspect.py
+++ b/sphinx/util/inspect.py
@@ -16,7 +16,7 @@ import sys
 inspect = __import__('inspect')
 
 from sphinx.util import force_decode
-from sphinx.util.pycompat import bytes
+from sphinx.util.pycompat import bytes, builtins
 
 
 if sys.version_info >= (3, 0):
@@ -151,6 +151,6 @@ def is_builtin_class_method(obj, attr_name):
     classes = [c for c in inspect.getmro(obj) if attr_name in c.__dict__]
     cls = classes[0] if classes else object
 
-    if not hasattr(__builtins__, cls.__name__):
+    if not hasattr(builtins, safe_getattr(cls, '__name__', '')):
         return False
-    return getattr(__builtins__, cls.__name__) is cls
+    return getattr(builtins, safe_getattr(cls, '__name__', '')) is cls
diff --git a/sphinx/util/pycompat.py b/sphinx/util/pycompat.py
index 1e5ea3145..5f6e59eeb 100644
--- a/sphinx/util/pycompat.py
+++ b/sphinx/util/pycompat.py
@@ -48,6 +48,8 @@ if sys.version_info >= (3, 0):
             # try to match ParseError details with SyntaxError details
             raise SyntaxError(err.msg, (filepath, lineno, offset, err.value))
         return unicode(tree)
+    from itertools import zip_longest  # Python 3 name
+    import builtins
 
 else:
     # Python 2
@@ -69,6 +71,9 @@ else:
     # error handler
     import locale
     sys_encoding = locale.getpreferredencoding()
+    # use Python 3 name
+    from itertools import izip_longest as zip_longest
+    import __builtin__ as builtins
 
 
 def execfile_(filepath, _globals):