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
diff --git a/Misc/NEWS.d/next/macOS/2026-03-13-08-49-26.gh-issue-145902.UiPZUw.rst b/Misc/NEWS.d/next/macOS/2026-03-13-08-49-26.gh-issue-145902.UiPZUw.rst
new file mode 100644
index 00000000000000..8208c4eb045f59
--- /dev/null
+++ b/Misc/NEWS.d/next/macOS/2026-03-13-08-49-26.gh-issue-145902.UiPZUw.rst
@@ -0,0 +1,2 @@
+Fix incorrect handling of division by zero so that Python consistently
+raises ``ZeroDivisionError`` as expected.