diff --git a/Misc/NEWS b/Misc/NEWS
index c786d24..72e1a0c 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -10,6 +10,10 @@
 Core and Builtins
 -----------------
 
+- Issue #12973: Fix overflow check that relied on undefined behaviour in
+  list_repeat.  This bug caused test_list to fail with recent versions
+  of Clang.
+
 - Issue #12904: os.utime, os.futimes, os.lutimes, and os.futimesat now write
   atime and mtime with nanosecond precision on modern POSIX platforms.
 
diff --git a/Objects/listobject.c b/Objects/listobject.c
index 2cd8642..cada708 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -58,7 +58,7 @@
     if (newsize == 0)
         new_allocated = 0;
     items = self->ob_item;
-    if (new_allocated <= ((~(size_t)0) / sizeof(PyObject *)))
+    if (new_allocated <= (PY_SIZE_MAX / sizeof(PyObject *)))
         PyMem_RESIZE(items, PyObject *, new_allocated);
     else
         items = NULL;
@@ -510,9 +510,9 @@
     PyObject *elem;
     if (n < 0)
         n = 0;
-    size = Py_SIZE(a) * n;
-    if (n && size/n != Py_SIZE(a))
+    if (n > 0 && Py_SIZE(a) > PY_SSIZE_T_MAX / n)
         return PyErr_NoMemory();
+    size = Py_SIZE(a) * n;
     if (size == 0)
         return PyList_New(0);
     np = (PyListObject *) PyList_New(size);