diff --git a/packages/ISO8601/ISO8601.0.2.5/opam b/packages/ISO8601/ISO8601.0.2.5/opam
index cf214df02929..7ffdd9a36179 100644
--- a/packages/ISO8601/ISO8601.0.2.5/opam
+++ b/packages/ISO8601/ISO8601.0.2.5/opam
@@ -26,4 +26,7 @@ install: [ make "install" ]
 
 remove: [ "ocamlfind" "remove" "ISO8601" ]
 
-depends: [ "ocamlfind" {build} ]
+depends: [
+  "ocamlfind" {build}
+  "ocamlbuild" {build}
+]