diff --git a/Dockerfile b/Dockerfile
index 273677b..9bc9729 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,6 +1,6 @@
 FROM ocaml/opam:ubuntu-20.04-ocaml-4.14 AS opam
 COPY mirage-unikernel-unipi-spt.opam /home/opam/opam-repository/packages/mirage-unikernel-unipi-spt/mirage-unikernel-unipi-spt.0.0.1~dev/opam
-RUN opam update && opam depext mirage-unikernel-unipi-spt && opam install mirage-unikernel-unipi-spt
+RUN apt update && opam update && opam depext mirage-unikernel-unipi-spt && opam install mirage-unikernel-unipi-spt
 RUN bindir="$(opam config var bin)"; cp $bindir/unipi.spt $bindir/solo5-elftool $bindir/solo5-spt .
 
 FROM ubuntu:20.04