diff --git a/index.js b/index.js
index 90e43f3..b89f046 100644
--- a/index.js
+++ b/index.js
@@ -170,6 +170,8 @@ class MongoTenant {
 
           index[0] = tenantAwareIndex;
         }
+        // Removes the possible preserveUniqueKey flag, that generates an validation error on MongoDB
+        delete index[1].preserveUniqueKey
       });
 
       // apply tenancy awareness to field level unique indexes