diff --git a/python-crypto-2.6.1-python3.12.patch b/python-crypto-2.6.1-python3.12.patch
new file mode 100644
index 0000000..914c638
--- /dev/null
+++ b/python-crypto-2.6.1-python3.12.patch
@@ -0,0 +1,61 @@
+--- src/_fastmath.c
++++ src/_fastmath.c
+@@ -70,11 +70,11 @@ longObjToMPZ (mpz_t m, PyLongObject * p)
+ 	mpz_init (temp);
+ 	mpz_init (temp2);
+ #ifdef IS_PY3K
+-	if (p->ob_base.ob_size > 0) {
+-		size = p->ob_base.ob_size;
++	if (Py_SIZE(p) > 0) {
++		size = Py_SIZE(p);
+ 		negative = 1;
+ 	} else {
+-		size = -p->ob_base.ob_size;
++		size = -Py_SIZE(p);
+ 		negative = -1;
+ 	}
+ #else
+@@ -89,7 +89,11 @@ longObjToMPZ (mpz_t m, PyLongObject * p)
+ 	mpz_set_ui (m, 0);
+ 	for (i = 0; i < size; i++)
+ 	{
++#if PY_VERSION_HEX < 0x030C0000
+ 		mpz_set_ui (temp, p->ob_digit[i]);
++#else
++		mpz_set_ui (temp, p->long_value.ob_digit[i]);
++#endif
+ #ifdef IS_PY3K
+ 		mpz_mul_2exp (temp2, temp, PyLong_SHIFT * i);
+ #else
+@@ -123,7 +127,11 @@ mpzToLongObj (mpz_t m)
+ 	for (i = 0; i < size; i++)
+ 	{
+ #ifdef IS_PY3K
++#if PY_VERSION_HEX < 0x030C0000
+ 		l->ob_digit[i] = (digit) (mpz_get_ui (temp) & PyLong_MASK);
++#else
++		l->long_value.ob_digit[i] = (digit) (mpz_get_ui (temp) & PyLong_MASK);
++#endif
+ 		mpz_fdiv_q_2exp (temp, temp, PyLong_SHIFT);
+ #else
+ 		l->ob_digit[i] = (digit) (mpz_get_ui (temp) & MASK);
+@@ -131,11 +139,19 @@ mpzToLongObj (mpz_t m)
+ #endif
+ 	}
+ 	i = size;
++#if PY_VERSION_HEX < 0x030C0000
+ 	while ((i > 0) && (l->ob_digit[i - 1] == 0))
++#else
++	while ((i > 0) && (l->long_value.ob_digit[i - 1] == 0))
++#endif
+ 		i--;
+ #ifdef IS_PY3K
++#if PY_VERSION_HEX < 0x03090000
+ 	l->ob_base.ob_size = i * sgn;
+ #else
++       Py_SET_SIZE(l, (Py_ssize_t)(i * sgn));
++#endif
++#else
+ 	l->ob_size = i * sgn;
+ #endif
+ 	mpz_clear (temp);
diff --git a/python-crypto.spec b/python-crypto.spec
index 1264476..1ca9648 100644
--- a/python-crypto.spec
+++ b/python-crypto.spec
@@ -7,7 +7,7 @@
 Summary:	Cryptography library for Python
 Name:		python-crypto
 Version:	2.6.1
-Release:	42%{?dist}
+Release:	43%{?dist}
 # Mostly Public Domain apart from parts of HMAC.py and setup.py, which are Python
 License:	Public Domain and Python
 URL:		http://www.pycrypto.org/
@@ -25,6 +25,7 @@ Patch9:		python-crypto-2.6.1-python3.11.patch
 Patch10:	python-crypto-2.6.1-python3only.patch
 Patch11:	python-crypto-2.6.1-no-distutils.patch
 Patch12:	python-crypto-2.6.1-SyntaxWarning.patch
+Patch13:	python-crypto-2.6.1-python3.12.patch
 BuildRequires:	coreutils
 BuildRequires:	findutils
 BuildRequires:	gcc
@@ -112,6 +113,9 @@ rm -rf src/libtom
 # Get rid of a SyntaxWarning in test_random.py
 %patch12
 
+# Fix Python 3.12 compatibility
+%patch13
+
 %build
 %global optflags %{optflags} -fno-strict-aliasing
 %py3_build
@@ -135,6 +139,9 @@ PYTHONPATH=%{buildroot}%{python3_sitearch} %{__python3} pct-speedtest.py
 %{python3_sitearch}/pycrypto-%{version}-py3.*.egg-info
 
 %changelog
+* Mon Mar 13 2023 Paul Howarth <paul@city-fan.org> - 2.6.1-43
+- Fix Python 3.12 compatibility (rhbz#2177718)
+
 * Fri Jan 20 2023 Fedora Release Engineering <releng@fedoraproject.org> - 2.6.1-42
 - Rebuilt for https://fedoraproject.org/wiki/Fedora_38_Mass_Rebuild