diff --git a/Source/WebKit/WebProcess/Extensions/API/Cocoa/WebExtensionAPIStorageAreaCocoa.mm b/Source/WebKit/WebProcess/Extensions/API/Cocoa/WebExtensionAPIStorageAreaCocoa.mm
index ca3ed1ca51e0..11afa6861903 100644
--- a/Source/WebKit/WebProcess/Extensions/API/Cocoa/WebExtensionAPIStorageAreaCocoa.mm
+++ b/Source/WebKit/WebProcess/Extensions/API/Cocoa/WebExtensionAPIStorageAreaCocoa.mm
@@ -173,8 +173,8 @@
         return;
     }
 
-    if (anyItemsExceedQuota(serializedData, webExtensionStorageAreaSyncQuotaBytesPerItem, &keyWithError)) {
-        *outExceptionString = toErrorString(nil, [NSString stringWithFormat:@"items[`%@`]", keyWithError], @"exceeded maximum size for a single item");
+    if (m_type == WebExtensionDataType::Sync && anyItemsExceedQuota(serializedData, webExtensionStorageAreaSyncQuotaBytesPerItem, &keyWithError)) {
+        *outExceptionString = toErrorString(nil, [NSString stringWithFormat:@"items[`%@`]", keyWithError], @"it exceeded maximum size for a single item");
         return;
     }
 
diff --git a/Tools/TestWebKitAPI/Tests/WebKitCocoa/WKWebExtensionAPIStorage.mm b/Tools/TestWebKitAPI/Tests/WebKitCocoa/WKWebExtensionAPIStorage.mm
index 20df874c7398..25efd65b306b 100644
--- a/Tools/TestWebKitAPI/Tests/WebKitCocoa/WKWebExtensionAPIStorage.mm
+++ b/Tools/TestWebKitAPI/Tests/WebKitCocoa/WKWebExtensionAPIStorage.mm
@@ -65,7 +65,7 @@
         @"browser.test.assertThrows(() => browser?.storage?.local?.set(), /A required argument is missing/i)",
         @"browser.test.assertThrows(() => browser?.storage?.local?.set([]), /'items' value is invalid, because an object is expected/i)",
         @"browser.test.assertThrows(() => browser?.storage?.local?.set({ 'key': () => { 'function' } }), /it is not JSON-serializable/i)",
-        @"browser.test.assertThrows(() => browser?.storage?.local?.set({ 'key': 'a'.repeat(8193) }), /exceeded maximum size for a single item/i)",
+        @"browser.test.assertThrows(() => browser?.storage?.sync?.set({ 'key': 'a'.repeat(8193) }), /exceeded maximum size for a single item/i)",
 
         @"browser.test.assertThrows(() => browser?.storage?.local?.remove(), /A required argument is missing/i)",
         @"browser.test.assertThrows(() => browser?.storage?.local?.remove({}), /'keys' value is invalid, because a string or an array of strings is expected, but an object was provided/i)",
@@ -215,6 +215,10 @@
         @"result = await browser?.storage?.local?.get('array')",
         @"browser.test.assertDeepEq(updatedArray, result?.array)",
 
+        // Ensure there isn't a maximum item quota if the storageArea isn't sync.
+        @"await browser.storage?.local?.clear()",
+        @"browser.test.assertSafeResolve(() => browser.storage?.local?.set({ 'key': 'a'.repeat(8193) }))",
+
         @"browser.test.notifyPass()",
     ]);