diff --git a/index.d.ts b/index.d.ts
index e349d0cd652..5576770d296 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -1365,7 +1365,7 @@ declare module 'mongoose' {
   }
 
   interface SchemaTypeOptions<T> {
-    type: T;
+    type?: T;
 
     /** Defines a virtual with the given name that gets/sets this path. */
     alias?: string;