diff --git a/sphinx/util/compat.py b/sphinx/util/compat.py
index 4d5e19964..56ac9e80f 100644
--- a/sphinx/util/compat.py
+++ b/sphinx/util/compat.py
@@ -27,7 +27,7 @@ def make_admonition(node_class, name, arguments, options, content, lineno,
         textnodes, messages = state.inline_text(title_text, lineno)
         admonition_node += nodes.title(title_text, '', *textnodes)
         admonition_node += messages
-        if options.has_key('class'):
+        if 'class' in options:
             classes = options['class']
         else:
             classes = ['admonition-' + nodes.make_id(title_text)]