diff --git a/Lib/typing.py b/Lib/typing.py
index 0a685d3..5351883 100644
--- a/Lib/typing.py
+++ b/Lib/typing.py
@@ -1716,11 +1716,11 @@
 
 
 # attributes prohibited to set in NamedTuple class syntax
-_prohibited = ('__new__', '__init__', '__slots__', '__getnewargs__',
+_prohibited = {'__new__', '__init__', '__slots__', '__getnewargs__',
                '_fields', '_field_defaults', '_field_types',
-               '_make', '_replace', '_asdict', '_source')
+               '_make', '_replace', '_asdict', '_source'}
 
-_special = ('__module__', '__name__', '__annotations__')
+_special = {'__module__', '__name__', '__annotations__'}
 
 
 class NamedTupleMeta(type):