diff --git a/src/types.ts b/src/types.ts
index cf182d00..1f2d97bf 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -16,7 +16,7 @@ export interface JSONObject {
 type ClassInstance = any;
 
 export type SerializableJSONValue =
-  | Symbol
+  | symbol
   | Set<SuperJSONValue>
   | Map<SuperJSONValue, SuperJSONValue>
   | undefined