diff --git a/dtool/src/interrogatedb/py_compat.h b/dtool/src/interrogatedb/py_compat.h
index c5474b21ee..20946e7f48 100644
--- a/dtool/src/interrogatedb/py_compat.h
+++ b/dtool/src/interrogatedb/py_compat.h
@@ -243,6 +243,18 @@ INLINE PyObject *PyObject_CallMethodOneArg(PyObject *obj, PyObject *name, PyObje
 }
 #endif
 
+/* Python 3.12 */
+
+#if PY_VERSION_HEX < 0x030C0000
+#  define PyLong_IsNonNegative(value) (Py_SIZE((value)) >= 0)
+#else
+INLINE bool PyLong_IsNonNegative(PyObject *value) {
+  int overflow = 0;
+  long longval = PyLong_AsLongAndOverflow(value, &overflow);
+  return overflow == 1 || longval >= 0;
+}
+#endif
+
 /* Other Python implementations */
 
 // _PyErr_OCCURRED is an undocumented macro version of PyErr_Occurred.
diff --git a/panda/src/putil/bitArray_ext.cxx b/panda/src/putil/bitArray_ext.cxx
index 215d920cb4..6e0d860238 100644
--- a/panda/src/putil/bitArray_ext.cxx
+++ b/panda/src/putil/bitArray_ext.cxx
@@ -32,7 +32,7 @@ __init__(PyObject *init_value) {
   }
 #endif
 
-  if (!PyLong_Check(init_value) || Py_SIZE(init_value) < 0) {
+  if (!PyLong_Check(init_value) || !PyLong_IsNonNegative(init_value)) {
     PyErr_SetString(PyExc_ValueError, "BitArray constructor requires a positive integer");
     return;
   }
@@ -88,7 +88,7 @@ __getstate__() const {
  */
 void Extension<BitArray>::
 __setstate__(PyObject *state) {
-  if (Py_SIZE(state) >= 0) {
+  if (PyLong_IsNonNegative(state)) {
     __init__(state);
   } else {
     PyObject *inverted = PyNumber_Invert(state);
diff --git a/panda/src/putil/doubleBitMask_ext.I b/panda/src/putil/doubleBitMask_ext.I
index b774f22096..748def0371 100644
--- a/panda/src/putil/doubleBitMask_ext.I
+++ b/panda/src/putil/doubleBitMask_ext.I
@@ -28,8 +28,7 @@ __init__(PyObject *init_value) {
     return;
   }
 #endif
-
-  if (!PyLong_Check(init_value) || Py_SIZE(init_value) < 0) {
+  if (!PyLong_Check(init_value) || !PyLong_IsNonNegative(init_value)) {
     PyErr_SetString(PyExc_ValueError, "DoubleBitMask constructor requires a positive integer");
     return;
   }
diff --git a/tests/putil/test_bitarray.py b/tests/putil/test_bitarray.py
index 5da2fdc725..293be8df74 100644
--- a/tests/putil/test_bitarray.py
+++ b/tests/putil/test_bitarray.py
@@ -32,6 +32,9 @@ def test_bitarray_pickle():
     ba = BitArray(123)
     assert ba == pickle.loads(pickle.dumps(ba, -1))
 
+    ba = BitArray(1 << 128)
+    assert ba == pickle.loads(pickle.dumps(ba, -1))
+
 
 def test_bitarray_has_any_of():
     ba = BitArray()