diff --git a/docs/3.x.x/guides/models.md b/docs/3.x.x/guides/models.md
index 50ca2245a8..48e4664901 100644
--- a/docs/3.x.x/guides/models.md
+++ b/docs/3.x.x/guides/models.md
@@ -56,7 +56,7 @@ If you're using SQL databases, you should use the native SQL constraints to appl
 
   - `required` (boolean) — if true adds a required validator for this property.
   - `unique` (boolean) — whether to define a unique index on this property.
-  - `index` (boolean) — adds an index on this property, this will use the default mongodb index for the type and will run in the background.
+  - `index` (boolean) — adds an index on this property, this will create a [single field index](https://docs.mongodb.com/manual/indexes/#single-field) that will run in the background.
   - `max` (integer) — checks if the value is greater than or equal to the given minimum.
   - `min` (integer) — checks if the value is less than or equal to the given maximum.