diff --git a/store.mjs b/store.mjs
index ffdd90bf0e..10bdad3626 100644
--- a/store.mjs
+++ b/store.mjs
@@ -66,7 +66,7 @@ export function derive(stores, fn) {
 	const single = !Array.isArray(stores);
 	if (single) stores = [stores];
 
-	const auto = fn.length === 1;
+	const auto = fn.length < 2;
 	let value = {};
 
 	return readable(set => {