diff --git a/z3.spec b/z3.spec
index 146f0de..98777d7 100644
--- a/z3.spec
+++ b/z3.spec
@@ -26,6 +26,7 @@ BuildRequires:  jpackage-utils
 BuildRequires:  ocaml
 BuildRequires:  ocaml-findlib
 BuildRequires:  ocaml-ocamldoc
+BuildRequires:  ocaml-num-devel
 BuildRequires:  python2-devel
 BuildRequires:  python2-setuptools
 
@@ -251,6 +252,7 @@ mv %{buildroot}%{_prefix}/lib/lib%{name}java.so %{buildroot}%{_libdir}/%{name}
 %changelog
 * Fri Nov 17 2017 Richard W.M. Jones <rjones@redhat.com> - 4.5.0-7
 - OCaml 4.06.0 rebuild.
+- Add dependency on ocaml-num.
 
 * Tue Aug 08 2017 Richard W.M. Jones <rjones@redhat.com> - 4.5.0-6
 - OCaml 4.05.0 rebuild.