diff --git a/lib/set.rb b/lib/set.rb
index 921f18f97b..a0e945e0a8 100644
--- a/lib/set.rb
+++ b/lib/set.rb
@@ -804,7 +804,8 @@ class SortedSet < Set
 
   def initialize(*args, &block) # :nodoc:
     SortedSet.setup
-    initialize(*args, &block)
+    @keys = nil
+    super
   end
 end