--- x/lib/xarray.c
+++ y/lib/xarray.c
@@ -390,6 +390,7 @@ static void *xas_alloc(struct xa_state *
 	XA_NODE_BUG_ON(node, shift > BITS_PER_LONG);
 	XA_NODE_BUG_ON(node, !list_empty(&node->private_list));
 	node->shift = shift;
+	BUG_ON(shift > BITS_PER_LONG);
 	node->count = 0;
 	node->nr_values = 0;
 	RCU_INIT_POINTER(node->parent, xas->xa_node);