diff --git a/Lib/fractions.py b/Lib/fractions.py
index c1b12e7a1c091c..a4bcb825017c49 100644
--- a/Lib/fractions.py
+++ b/Lib/fractions.py
@@ -203,7 +203,7 @@ class Fraction(numbers.Rational):
     __slots__ = ('_numerator', '_denominator')
 
     # We're immutable, so use __new__ not __init__
-    def __new__(cls, numerator=0, denominator=None):
+    def __new__(cls, numerator=0, denominator=1):
         """Constructs a Rational.
 
         Takes a string like '3/2' or '1.5', another Rational instance, a