diff --git a/caisar.opam b/caisar.opam
index 60e13a6be66cd8713e6761e7332afea6635a3806..1057e0bdd91d913ef5003c64fe679403abc8a14a 100644
--- a/caisar.opam
+++ b/caisar.opam
@@ -29,7 +29,7 @@ depends: [
   "menhirLib" {>= "20210310"}
   "ppx_deriving_yojson" {>= "3.6.1"}
   "csv" {>= "2.4"}
-  "why3" {>= "1.5.0"}
+  "why3" {= "1.5.1"}
   "re" {>= "1.10.4"}
   "caisar-nnet" {= version}
   "caisar-ovo" {= version}
diff --git a/dune-project b/dune-project
index 8d1d7d4e4b5e30813740dba7765442460b82774c..e72f7f96d16594553d0b03e11968a9787098af7a 100644
--- a/dune-project
+++ b/dune-project
@@ -82,7 +82,7 @@
    (menhirLib (>= 20210310))
    (ppx_deriving_yojson (>= 3.6.1))
    (csv (>= 2.4))
-   (why3 (>= 1.5.0))
+   (why3 (= 1.5.1))
    (re (>= 1.10.4))
    (caisar-nnet (= :version))
    (caisar-ovo (= :version))