diff --git a/store.mjs b/store.mjs
index 797b512704..10bdad3626 100644
--- a/store.mjs
+++ b/store.mjs
@@ -66,6 +66,7 @@ export function derive(stores, fn) {
 	const single = !Array.isArray(stores);
 	if (single) stores = [stores];
 
+	const auto = fn.length < 2;
 	let value = {};
 
 	return readable(set => {
@@ -77,7 +78,7 @@ export function derive(stores, fn) {
 		const sync = () => {
 			if (pending) return;
 			const result = fn(single ? values[0] : values, set);
-			if (value !== (value = result)) set(result);
+			if (auto && (value !== (value = result))) set(result);
 		}
 
 		const unsubscribers = stores.map((store, i) => store.subscribe(