diff --git a/src/error/GraphQLError.ts b/src/error/GraphQLError.ts
index b88d27a56c..c7cde504dc 100644
--- a/src/error/GraphQLError.ts
+++ b/src/error/GraphQLError.ts
@@ -17,7 +17,7 @@ import type { Source } from '../language/source';
  * an object which can contain all the values you need.
  */
 export interface GraphQLErrorExtensions {
-  [attributeName: string]: unknown;
+  [attributeName: string | symbol]: unknown;
 }
 
 export interface GraphQLErrorOptions {