diff --git a/.gitignore b/.gitignore
index d7c6275..ef707d2 100644
--- a/.gitignore
+++ b/.gitignore
@@ -14,4 +14,6 @@
 .glide/
 
 .idea/
+.vscode/
+vendor/
 *.iml
\ No newline at end of file
diff --git a/adapter.go b/adapter.go
index 2140a48..190a6fa 100644
--- a/adapter.go
+++ b/adapter.go
@@ -146,7 +146,8 @@ func (a *adapter) open(databaseName string) error {
 	if _, err = collection.Indexes().CreateOne(
 		context.Background(),
 		mongo.IndexModel{
-			Keys: keysDoc,
+			Keys:    keysDoc,
+			Options: options.Index().SetUnique(true),
 		},
 	); err != nil {
 		return err