diff --git a/test/types/models.test.ts b/test/types/models.test.ts
index ff473840f1c..2e46de6eb76 100644
--- a/test/types/models.test.ts
+++ b/test/types/models.test.ts
@@ -853,3 +853,19 @@ async function gh14003() {
   await TestModel.validate({ name: 'foo' }, ['name']);
   await TestModel.validate({ name: 'foo' }, { pathsToSkip: ['name'] });
 }
+
+async function gh13999() {
+  class RepositoryBase<T> {
+    protected model: mongoose.Model<T>;
+
+    constructor(schemaModel: mongoose.Model<T>) {
+      this.model = schemaModel;
+    }
+
+    async insertMany(elems: T[]): Promise<T[]> {
+      elems = await this.model.insertMany(elems, { session: null });
+      return elems;
+    }
+  }
+
+}
diff --git a/types/models.d.ts b/types/models.d.ts
index 45f67138b46..2df347c9843 100644
--- a/types/models.d.ts
+++ b/types/models.d.ts
@@ -395,6 +395,10 @@ declare module 'mongoose' {
       docs: Array<TRawDocType>,
       options: InsertManyOptions & { rawResult: true; }
     ): Promise<mongodb.InsertManyResult<Require_id<THydratedDocumentType>>>;
+    insertMany(
+      doc: Array<TRawDocType>,
+      options: InsertManyOptions
+    ): Promise<Array<THydratedDocumentType>>;
     insertMany<DocContents = TRawDocType>(
       docs: Array<DocContents | TRawDocType>,
       options: InsertManyOptions & { lean: true; }