diff --git a/src/rrd2csv.ml b/src/rrd2csv.ml
index e3d6a83..06aec7b 100644
--- a/src/rrd2csv.ml
+++ b/src/rrd2csv.ml
@@ -12,6 +12,7 @@
  * GNU Lesser General Public License for more details.
  *)
 
+open Stdext
 open Pervasiveext
 open Xstringext
 open Listext