diff --git a/src/ldap_ooclient.ml b/src/ldap_ooclient.ml
index 79fd51d..7ffa39e 100644
--- a/src/ldap_ooclient.ml
+++ b/src/ldap_ooclient.ml
@@ -23,7 +23,7 @@
 open Ldap_types
 open Ldap_funclient
 open Ldap_schemaparser
-open String
+let lowercase = String.lowercase
 
 (* types used throughout the library *)
 (* add types *)