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diff --git a/Misc/NEWS.d/next/Library/2025-04-29-11-48-46.gh-issue-132876.lyTQGZ.rst b/Misc/NEWS.d/next/Library/2025-04-29-11-48-46.gh-issue-132876.lyTQGZ.rst
 ``ldexp()`` on Windows doesn't round subnormal results before Windows 11,
 but should.  Python's :func:`math.ldexp` wrapper now does round them, so
 results may change slightly, in rare cases of very small results, on
 Windows versions before 11.
diff --git a/Modules/mathmodule.c b/Modules/mathmodule.c
    } else {
        errno = 0;
        r = ldexp(x, (int)exp);
 #ifdef _MSC_VER
        if (DBL_MIN > r && r > -DBL_MIN) {
            /* Denormal (or zero) results can be incorrectly rounded here (rather,
               truncated).  Fixed in newer versions of the C runtime, included
               with Windows 11. */
            int original_exp;
            frexp(x, &original_exp);
            if (original_exp > DBL_MIN_EXP) {
                /* Shift down to the smallest normal binade.  No bits lost. */
                int shift = DBL_MIN_EXP - original_exp;
                x = ldexp(x, shift);
                exp -= shift;
            }
            /* Multiplying by 2**exp finishes the job, and the HW will round as
               appropriate.  Note: if exp < -DBL_MANT_DIG, all of x is shifted
               to be < 0.5ULP of smallest denorm, so should be thrown away.  If
               exp is so very negative that ldexp underflows to 0, that's fine;
               no need to check in advance. */
            r = x*ldexp(1.0, (int)exp);
        }
 #endif
        if (isinf(r))
            errno = ERANGE;
    }
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,4 @@
		``ldexp()`` on Windows doesn't round subnormal results before Windows 11,
		but should. Python's :func:`math.ldexp` wrapper now does round them, so
		results may change slightly, in rare cases of very small results, on
		Windows versions before 11.
Original file line number	Diff line number	Diff line change
Expand Up		@@ -2163,6 +2163,27 @@ math_ldexp_impl(PyObject module, double x, PyObject i)
		} else {
		errno = 0;
		r = ldexp(x, (int)exp);
		#ifdef _MSC_VER
		if (DBL_MIN > r && r > -DBL_MIN) {
		/* Denormal (or zero) results can be incorrectly rounded here (rather,
		truncated). Fixed in newer versions of the C runtime, included
		with Windows 11. */
		int original_exp;
		frexp(x, &original_exp);
		if (original_exp > DBL_MIN_EXP) {
		/* Shift down to the smallest normal binade. No bits lost. */
		int shift = DBL_MIN_EXP - original_exp;
		x = ldexp(x, shift);
		exp -= shift;
		}
		/* Multiplying by 2**exp finishes the job, and the HW will round as
		appropriate. Note: if exp < -DBL_MANT_DIG, all of x is shifted
		to be < 0.5ULP of smallest denorm, so should be thrown away. If
		exp is so very negative that ldexp underflows to 0, that's fine;
		no need to check in advance. */
		r = x*ldexp(1.0, (int)exp);
		}
		#endif
		if (isinf(r))
		errno = ERANGE;
		}
Expand Down