--- a/util/promise.lua	Sat Nov 16 16:45:33 2019 +0100
+++ b/util/promise.lua	Sat Nov 16 16:52:31 2019 +0100
@@ -49,6 +49,9 @@
 	for _, cb in ipairs(cbs) do
 		cb(value);
 	end
+	-- No need to keep references to callbacks
+	promise._pending_on_fulfilled = nil;
+	promise._pending_on_rejected = nil;
 	return true;
 end