diff --git a/ocaml-gettext.spec b/ocaml-gettext.spec
index 123c2b9..41c6f98 100644
--- a/ocaml-gettext.spec
+++ b/ocaml-gettext.spec
@@ -17,6 +17,7 @@ BuildRequires:  ocaml-compiler-libs
 BuildRequires:  ocaml-ocamldoc
 BuildRequires:  ocaml-fileutils-devel >= 0.4.4-4
 BuildRequires:  ocaml-dune-devel
+BuildRequires:  ocaml-cppo
 BuildRequires:  docbook-style-xsl
 BuildRequires:  libxslt
 BuildRequires:  libxml2
@@ -182,6 +183,7 @@ rm -rf $RPM_BUILD_ROOT/usr/doc
 * Tue Mar  2 23:22:35 GMT 2021 Richard W.M. Jones <rjones@redhat.com> - 0.4.2-1
 - New upstream version 4.2
 - Remove patch now upstream.
+- BR ocaml-cppo
 
 * Mon Mar  1 23:22:35 GMT 2021 Richard W.M. Jones <rjones@redhat.com> - 0.4.1-9
 - OCaml 4.12.0 build