diff --git a/packages/runtime-dom/src/helpers/useCssVars.ts b/packages/runtime-dom/src/helpers/useCssVars.ts
index ff90ec8ce..1f5ac7fae 100644
--- a/packages/runtime-dom/src/helpers/useCssVars.ts
+++ b/packages/runtime-dom/src/helpers/useCssVars.ts
@@ -30,7 +30,7 @@ export function useCssVars(
 
   const setVars = () =>
     setVarsOnVNode(instance.subTree, getter(instance.proxy!), prefix)
-  onMounted(() => watchEffect(setVars))
+  onMounted(() => watchEffect(setVars, { flush: 'post' }))
   onUpdated(setVars)
 }