diff --git a/Modules/arraymodule.c b/Modules/arraymodule.c
index 6dc46ad..256bcd8 100644
--- a/Modules/arraymodule.c
+++ b/Modules/arraymodule.c
@@ -735,6 +735,14 @@
 		ihigh = Py_SIZE(a);
 	item = a->ob_item;
 	d = n - (ihigh-ilow);
+	/* Issue #4509: If the array has exported buffers and the slice
+	   assignment would change the size of the array, fail early to make
+	   sure we don't modify it. */
+	if (d != 0 && a->ob_exports > 0) {
+		PyErr_SetString(PyExc_BufferError, 
+			"cannot resize an array that is exporting buffers");
+		return -1;
+	}
 	if (d < 0) { /* Delete -d items */
 		memmove(item + (ihigh+d)*a->ob_descr->itemsize,
 			item + ihigh*a->ob_descr->itemsize,