fix argument receiver of Slop#respond_to? for second argument

Test Suite:
  * 407348e48071e0e91fd999976d58c22577cc0554

1 files changed, 1 insertions, 1 deletions

diff --git a/lib/slop.rb b/lib/slop.rb
index 7f60472..908cb4b 100644
--- a/lib/slop.rb
+++ b/lib/slop.rb
@@ -292,7 +292,7 @@ class Slop
   # Override this method so we can check if an option? method exists.
   #
   # Returns true if this option key exists in our list of options.
-  def respond_to?(method)
+  def respond_to?(method, include_private = false)
     method = method.to_s
     if method.end_with?('?') && options.any? { |o| o.key == method.chop }
       true