diff --git a/Lib/test/test_capi.py b/Lib/test/test_capi.py
index 612e639846d..4d931f8d3c6 100644
--- a/Lib/test/test_capi.py
+++ b/Lib/test/test_capi.py
@@ -67,6 +67,14 @@ def __len__(self):
                 return 1
         self.assertRaises(TypeError, _posixsubprocess.fork_exec,
                           1,Z(),3,[1, 2],5,6,7,8,9,10,11,12,13,14,15,16,17)
+        # Issue #15736: overflow in _PySequence_BytesToCharpArray()
+        class Z(object):
+            def __len__(self):
+                return sys.maxsize
+            def __getitem__(self, i):
+                return b'x'
+        self.assertRaises(MemoryError, _posixsubprocess.fork_exec,
+                          1,Z(),3,[1, 2],5,6,7,8,9,10,11,12,13,14,15,16,17)
 
     @unittest.skipUnless(_posixsubprocess, '_posixsubprocess required for this test.')
     def test_subprocess_fork_exec(self):
diff --git a/Objects/abstract.c b/Objects/abstract.c
index 299daf549ef..7705d05d71e 100644
--- a/Objects/abstract.c
+++ b/Objects/abstract.c
@@ -2728,6 +2728,13 @@ _PySequence_BytesToCharpArray(PyObject* self)
     if (argc == -1)
         return NULL;
 
+    assert(argc >= 0);
+
+    if ((size_t)argc > (PY_SSIZE_T_MAX-sizeof(char *)) / sizeof(char *)) {
+        PyErr_NoMemory();
+        return NULL;
+    }
+
     array = malloc((argc + 1) * sizeof(char *));
     if (array == NULL) {
         PyErr_NoMemory();