diff --git a/opam b/opam
index 4543d82ace8890fde246d0f1d3dee3a67ea59f80..a72a1319bd11b9b2b3c791dc34698f7cc080e823 100644
--- a/opam
+++ b/opam
@@ -121,6 +121,7 @@ depends: [
   "menhir" { >= "20181006" & build }
   "ocaml" { >= "4.11.1" }
   "ocamlgraph" { >= "1.8.8" }
+  "unionFind" { >= "20220107" }
   "why3" { >= "1.6.0" }
   "yaml" { >= "3.0.0" }
   "yojson" {>= "1.6.0" & (>= "2.0.1" | !with-test)}