diff --git a/caisar.opam b/caisar.opam
index 3a0158d6f7109399c6c998e0316f63fd07c46533..04f8e424d3b5f7d920482b6ac14e88b70f5d102d 100644
--- a/caisar.opam
+++ b/caisar.opam
@@ -20,7 +20,7 @@ depends: [
   "menhirLib" {>= "20210310"}
   "ppx_deriving_yojson" {>= "3.6.1"}
   "csv" {>= "2.4"}
-  "why3" {>= "1.4"}
+  "why3" {= "1.4.0"}
   "re"
   "onnx"
   "odoc" {with-doc}
diff --git a/dune-project b/dune-project
index c0e7bd02c1cfce445db33902de2f142a99a6afde..1792e8746af599944bad3faf7cdf165f1dd89a40 100644
--- a/dune-project
+++ b/dune-project
@@ -30,7 +30,7 @@
    (menhirLib (>= 20210310))
    (ppx_deriving_yojson (>= 3.6.1))
    (csv (>= 2.4))
-   (why3 (>= 1.4))
+   (why3 (= 1.4.0))
    re
    onnx
   )