diff --git a/src/runtime/transition/index.ts b/src/runtime/transition/index.ts
index 8f5a9521b6..9315cd77d5 100644
--- a/src/runtime/transition/index.ts
+++ b/src/runtime/transition/index.ts
@@ -212,7 +212,20 @@ type ClientRectMap = Map<any, { rect: ClientRect }>;
 
 export function crossfade({ fallback, ...defaults }: CrossfadeParams & {
 	fallback?: (node: Element, params: CrossfadeParams, intro: boolean) => TransitionConfig;
-}) {
+}): [
+  (
+    node: Element,
+    params: CrossfadeParams & {
+      key: any;
+    }
+  ) => () => TransitionConfig,
+  (
+    node: Element,
+    params: CrossfadeParams & {
+      key: any;
+    }
+  ) => () => TransitionConfig
+] {
 	const to_receive: ClientRectMap = new Map();
 	const to_send: ClientRectMap = new Map();