diff --git a/ocp-indent/Dockerfile b/ocp-indent/Dockerfile
index 3971932..14f2f9d 100644
--- a/ocp-indent/Dockerfile
+++ b/ocp-indent/Dockerfile
@@ -1,10 +1,11 @@
-FROM ocaml/opam
+FROM ocaml/opam2
 
 SHELL ["/bin/bash", "-lc"]
 LABEL io.whalebrew.name 'ocp-indent'
 LABEL io.whalebrew.config.working_dir '/workdir'
 WORKDIR /workdir
 
+RUN sudo apt-get install m4 --yes
 RUN opam install --yes ocp-indent
 RUN ocp-indent --help