diff --git a/libnbd.spec b/libnbd.spec
index b39487b..7225f6e 100644
--- a/libnbd.spec
+++ b/libnbd.spec
@@ -45,6 +45,7 @@ BuildRequires:  python3-devel
 # For the OCaml bindings.
 BuildRequires:  ocaml
 BuildRequires:  ocaml-findlib-devel
+BuildRequires:  ocaml-ocamldoc
 
 # Only for building the examples.
 BuildRequires:  glib2-devel