Basic.sort_key fix

gistfile1.txt

diff --git a/sympy/core/basic.py b/sympy/core/basic.py
index ceeff1c..eac8670 100644
--- a/sympy/core/basic.py
+++ b/sympy/core/basic.py
@@ -311,7 +311,7 @@ def sort_key(self, order=None):
 
         """
         from sympy.core.singleton import S
-        return self.class_key(), (len(self.args), self.args), S.One.sort_key(), S.One
+        return self.class_key(), (len(self.args), tuple([i.sort_key() for i in self.args])), S.One.sort_key(), S.One
 
 
     def __eq__(self, other):