--- a/util/promise.lua	Thu Oct 18 12:04:14 2018 +0100
+++ b/util/promise.lua	Thu Oct 18 12:11:50 2018 +0100
@@ -46,7 +46,9 @@
 	local function _reject(e)
 		if resolved then return; end
 		resolved = true;
-		if promise_settle(p, "rejected", next_rejected, p._pending_on_rejected, e) then
+		if is_promise(e) then
+			e:next(new_resolve_functions(p));
+		elseif promise_settle(p, "rejected", next_rejected, p._pending_on_rejected, e) then
 			p.reason = e;
 		end
 	end