diff --git a/src/internal/struct.ts b/src/internal/struct.ts
index 9073957..8cb3857 100644
--- a/src/internal/struct.ts
+++ b/src/internal/struct.ts
@@ -76,6 +76,9 @@ export function _polyfill_contextMetadata(target: object): void {
 	if (!Symbol?.metadata) {
 		return;
 	}
+	if (Symbol.metadata in target) {
+		return;
+	}
 	Object.defineProperty(target, Symbol.metadata, {
 		enumerable: true,
 		configurable: true,