diff --git a/.build.yml b/.build.yml
index 5c9a6d2..2e372d1 100644
--- a/.build.yml
+++ b/.build.yml
@@ -5,7 +5,9 @@ sources:
   - https://git.sr.ht/~iptq/logical-foundations
 tasks:
   - setup: |
-      opam install coq=8.8.1
+      opam init -yc 4.09.1
+      opam install -y coq=8.8.1
   - build: |
+      eval $(opam env)
       cd logical-foundations
       make