diff --git a/dune-project b/dune-project
index 3372dc4..28ed13f 100644
--- a/dune-project
+++ b/dune-project
@@ -30,12 +30,12 @@
   (core_unix
    (and
     :with-test
-    (>= v0.15)
-    (< v0.16)))
+    (>= v0.14)
+    (< v0.15)))
   (core
    (and
-    (>= v0.15)
-    (< v0.16)))
+    (>= v0.14)
+    (< v0.15)))
   bignum
   michelson-adt
   michelson-parser))
diff --git a/tezla.opam b/tezla.opam
index b149ddc..048ec52 100644
--- a/tezla.opam
+++ b/tezla.opam
@@ -13,8 +13,8 @@ depends: [
   "alcotest" {with-test}
   "qcheck" {with-test}
   "qcheck-alcotest" {with-test}
-  "core_unix" {with-test & >= "v0.15" & < "v0.16"}
-  "core" {>= "v0.15" & < "v0.16"}
+  "core_unix" {with-test & >= "v0.14" & < "v0.15"}
+  "core" {>= "v0.14" & < "v0.15"}
   "bignum"
   "michelson-adt"
   "michelson-parser"