diff --git a/packages/virtual-core/src/index.ts b/packages/virtual-core/src/index.ts
index 785f3421..28001a8a 100644
--- a/packages/virtual-core/src/index.ts
+++ b/packages/virtual-core/src/index.ts
@@ -619,7 +619,7 @@ export class Virtualizer<
 
         if (!measureElement) {
           measureElement = (node: TItemElement | null | undefined) => {
-            const key = getItemKey(i)
+            const key = this.options.getItemKey(i)
             const prevNode = this.elementsCache.get(key)
 
             if (!node) {
@@ -751,9 +751,8 @@ export class Virtualizer<
     entry: ResizeObserverEntry | undefined,
   ) => {
     const i = this.indexFromElement(node)
-    const item = this.getMeasurements()[i]
 
-    if (!item || !node.isConnected) {
+    if (!node.isConnected) {
       this.elementsCache.forEach((cached, key) => {
         if (cached === node) {
           this.observer.unobserve(node)
@@ -763,14 +762,16 @@ export class Virtualizer<
       return
     }
 
-    const prevNode = this.elementsCache.get(item.key)
+    const itemKey = this.options.getItemKey(i)
+
+    const prevNode = this.elementsCache.get(itemKey)
 
     if (prevNode !== node) {
       if (prevNode) {
         this.observer.unobserve(prevNode)
       }
       this.observer.observe(node)
-      this.elementsCache.set(item.key, node)
+      this.elementsCache.set(itemKey, node)
     }
 
     this.resizeItem(i, this.options.measureElement(node, entry, this))