diff --git a/packages/cacheable/src/index.ts b/packages/cacheable/src/index.ts
index 1410bd31..2f2846a2 100644
--- a/packages/cacheable/src/index.ts
+++ b/packages/cacheable/src/index.ts
@@ -1155,10 +1155,17 @@ export class Cacheable extends Hookified {
 		const primaryBackfillBarrier = this.cancelPrimaryBackfills(keys);
 		await primaryBackfillBarrier;
 		if (this.stats.enabled) {
-			const statResult = (await this._primary.get(keys)) as unknown;
-			for (const key of keys) {
+			// Use the raw entries, because a cached value can be undefined.
+			const statResults = await this._primary.getManyRaw<unknown>(keys);
+			for (const [index, key] of keys.entries()) {
+				// Skip a key that is not in the cache. Size only the value of this key.
+				const statResult = statResults[index];
+				if (statResult === undefined) {
+					continue;
+				}
+
 				this.stats.decreaseKSize(key);
-				this.stats.decreaseVSize(statResult);
+				this.stats.decreaseVSize(statResult.value);
 				this.stats.decreaseCount();
 				this.stats.incrementDeletes();
 			}
diff --git a/packages/cacheable/test/index.test.ts b/packages/cacheable/test/index.test.ts
index 214f275c..1318cbc0 100644
--- a/packages/cacheable/test/index.test.ts
+++ b/packages/cacheable/test/index.test.ts
@@ -1095,12 +1095,19 @@ describe("cacheable stats enabled", async () => {
 	test("should get stats on delete many", async () => {
 		const cacheable = new Cacheable({ stats: true });
 		await cacheable.setMany([
-			{ key: "key1", value: "value1" },
-			{ key: "key2", value: "value2" },
+			{ key: "key1", value: { id: "value1" } },
+			{ key: "key2", value: undefined },
+			{ key: "key3", value: { id: "value3" } },
 		]);
-		await cacheable.deleteMany(["key1", "key2"]);
+		// The stats of a cache that holds only key3 are the expected result.
+		const expected = new Cacheable({ stats: true });
+		await expected.set("key3", { id: "value3" });
+
+		await cacheable.deleteMany(["key1", "key2", "missing"]);
 		expect(cacheable.stats.deletes).toBe(2);
-		expect(cacheable.stats.count).toBe(0);
+		expect(cacheable.stats.count).toBe(1);
+		expect(cacheable.stats.ksize).toBe(expected.stats.ksize);
+		expect(cacheable.stats.vsize).toBe(expected.stats.vsize);
 	});
 	test("should get stats on clear", async () => {
 		const cacheable = new Cacheable({ stats: true });
diff --git a/packages/utils/src/stats.ts b/packages/utils/src/stats.ts
index 0e23a992..9eba5d58 100644
--- a/packages/utils/src/stats.ts
+++ b/packages/utils/src/stats.ts
@@ -483,7 +483,8 @@ export class Stats {
 	}
 
 	public roughSizeOfObject(object: any): number {
-		const objectList: any[] = [];
+		// Use a Set so that the visited check is O(1) and the full walk stays linear.
+		const objectList = new Set<any>();
 		const stack: any[] = [object];
 		let bytes = 0;
 
@@ -504,12 +505,12 @@ export class Stats {
 				}
 
 				// Check for circular references - if this object was already processed, skip it
-				if (objectList.includes(value)) {
+				if (objectList.has(value)) {
 					continue;
 				}
 
 				// object as default
-				objectList.push(value);
+				objectList.add(value);
 
 				// Estimate object overhead, and then recursively estimate the size of properties
 				for (const key in value) {