diff --git a/src/context/context.ts b/src/context/context.ts
index 2619be6b6..959a1d8f2 100644
--- a/src/context/context.ts
+++ b/src/context/context.ts
@@ -155,10 +155,10 @@ export class Context {
   }
 }
 
-const BLOCKED_SCOPE_KEYS = new Set(['__proto__', 'constructor', 'prototype'])
+const BLOCKED_SCOPE_KEYS: ReadonlySet<PropertyKey> = new Set(['__proto__', 'constructor', 'prototype'])
 
 export function readJSProperty (obj: Scope, key: PropertyKey, ownPropertyOnly: boolean) {
-  if (typeof key === 'string' && BLOCKED_SCOPE_KEYS.has(key)) {
+  if (BLOCKED_SCOPE_KEYS.has(key)) {
     if (ownPropertyOnly || !hasOwnProperty.call(obj, key)) return undefined
   }
   if (ownPropertyOnly && !hasOwnProperty.call(obj, key) && !(obj instanceof Drop)) return undefined