diff --git a/index.d.ts b/index.d.ts
index 653f4b5..b4efe49 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -18,7 +18,7 @@ declare module 'apollo-datasource-mongodb' {
     : Collection<T>
   
   export interface Fields {
-    [fieldName: string]: string | number | boolean | [string | number | boolean]
+    [fieldName: string]: string | number | boolean | (string | number | boolean)[]
   }
 
   export interface Options {
@@ -51,4 +51,4 @@ declare module 'apollo-datasource-mongodb' {
 
     deleteFromCacheById(id: ObjectId | string): Promise<void>
   }
-}
\ No newline at end of file
+}