diff --git a/theme/src/client/composables/outline.ts b/theme/src/client/composables/outline.ts
index ffa75d8f..ebb4319a 100644
--- a/theme/src/client/composables/outline.ts
+++ b/theme/src/client/composables/outline.ts
@@ -187,7 +187,7 @@ export function useActiveAnchor(container: Ref<HTMLElement | null>, marker: Ref<
     if (!isAsideEnabled.value)
       return
 
-    const scrollY = window.scrollY
+    const scrollY = Math.round(window.scrollY)
     const innerHeight = window.innerHeight
     const offsetHeight = document.body.offsetHeight
     const isBottom = Math.abs(scrollY + innerHeight - offsetHeight) < 1
@@ -222,7 +222,7 @@ export function useActiveAnchor(container: Ref<HTMLElement | null>, marker: Ref<
     // find the last header above the top of viewport
     let activeLink: string | null = null
     for (const { link, top } of headers) {
-      if (top > scrollY + 88)
+      if (top > scrollY + 92)
         break
 
       activeLink = link
@@ -284,18 +284,14 @@ export function useActiveAnchor(container: Ref<HTMLElement | null>, marker: Ref<
 
 function getAbsoluteTop(element: HTMLElement): number {
   let offsetTop = 0
-  while (element !== document.body) {
-    if (element === null) {
-      // child element is:
-      // - not attached to the DOM (display: none)
-      // - set to fixed position (not scrollable)
-      // - body or html element (null offsetParent)
-      return Number.NaN
+  while (element && element !== document.body) {
+    if (window.getComputedStyle(element).position === 'fixed') {
+      return element.offsetTop
     }
     offsetTop += element.offsetTop
     element = element.offsetParent as HTMLElement
   }
-  return offsetTop
+  return element ? offsetTop : Number.NaN
 }
 
 /**