diff --git a/src/runtime/transition/index.ts b/src/runtime/transition/index.ts
index 7cb38fbaaa..eadcec0214 100644
--- a/src/runtime/transition/index.ts
+++ b/src/runtime/transition/index.ts
@@ -107,7 +107,7 @@ export function slide(node: Element, {
 	easing = cubicOut,
 	axis = 'y'
 }: SlideParams = {}): TransitionConfig {
-	const direction = { x: axis === 'x' ? 1 : 0, y: axis === 'y' ? 1 : 0 };
+	const direction: { x: 1 | 0, y: 1 | 0 } = { x: axis === 'x' ? 1 : 0, y: axis === 'y' ? 1 : 0 };
 	const style = getComputedStyle(node);
 	const opacity = +style.opacity;
 	const height = parseFloat(style.height);