diff --git a/__tests__/priceService.test.ts b/__tests__/priceService.test.ts
index 468641f..2ee36f9 100644
--- a/__tests__/priceService.test.ts
+++ b/__tests__/priceService.test.ts
@@ -94,7 +94,7 @@ describe('Price Service', () => {
   test('ItemPriceData.toString() returns formatted string', () => {
     const data = new ItemPriceData()
     data.sku = mockSku
-    data.update = mockDate
+    data.update = mockDate.getTime()
     data.ttl = mockTtl
     data.keys = 1
     data.metal = 10.66
@@ -102,6 +102,8 @@ describe('Price Service', () => {
 
     const result = data.toString()
     expect(result).toContain(`Price for ${mockSku}`)
+    expect(result).toContain(mockDate.toString())
+    expect(result).toContain(new Date(mockDate.getTime() + mockTtl).toString())
     expect(result).toContain(`"keys":${data.keys}`)
     expect(result).toContain(`"metal":${data.metal}`)
     expect(result).toContain(`"scmPrice":${data.scmPrice}`)
diff --git a/src/content/content.ts b/src/content/content.ts
index a8ce368..c41d706 100644
--- a/src/content/content.ts
+++ b/src/content/content.ts
@@ -250,7 +250,7 @@ async function inject() {
 		}).reverse().forEach((element) => {
 			priceInfoboxHeadingRow.insertAdjacentElement('afterend', element.row);
 		})
-		if(!updateTime) { updateTime = new Date() }
+		if(!updateTime || !(updateTime instanceof Date) || isNaN(+updateTime)) updateTime = new Date()
 
 		// Footer row
 		const row = document.createElement("tr");
diff --git a/src/content/priceService.ts b/src/content/priceService.ts
index 0fe7eaa..5aa675d 100644
--- a/src/content/priceService.ts
+++ b/src/content/priceService.ts
@@ -7,8 +7,8 @@ import { logDebug, log } from "./utils/log"
 export class ItemPriceData {
 	/** Item SKU. */
 	sku: string
-	/** Date updated. */
-	update: Date
+	/** Date updated, as Unix timestamp. */
+	update: number
 	/** TTL in milliseconds. */
 	ttl: number
 	/** Price in keys. */
@@ -19,7 +19,7 @@ export class ItemPriceData {
 	scmPrice: number
 
 	toString(): string {
-		return `Price for ${this.sku}, fetched ${this.update} (expires ${this.update.getTime() + this.ttl})\n` + 
+		return `Price for ${this.sku}, fetched ${new Date(this.update)} (expires ${new Date(this.update + this.ttl)})\n` + 
 			JSON.stringify({
 				keys: this.keys,
 				metal: this.metal,
@@ -43,8 +43,8 @@ export async function fetchPrice(token: string, sku: string, update: Date = new
 	return new Promise(async (resolve, reject) => {
 		var data: ItemPriceData | null
 
-		const cached = await getStorageValue(storage_priceprefix + sku, null)
-		if (cached != null && 'keys' in cached && 'metal' in cached) {
+		const cached: ItemPriceData = await getStorageValue(storage_priceprefix + sku, null)
+		if (cached != null && 'keys' in cached && 'metal' in cached && !isNaN(cached.update)) {
 			data = cached
 		}
 
@@ -55,7 +55,7 @@ export async function fetchPrice(token: string, sku: string, update: Date = new
 			}
 			data = new ItemPriceData()
 			data.sku = sku
-			data.update = update
+			data.update = update.getTime()
 			data.ttl = ttl
 
 			try {