diff --git a/webauthn.opam b/webauthn.opam
index def2a48..8d5a1ad 100644
--- a/webauthn.opam
+++ b/webauthn.opam
@@ -30,7 +30,7 @@ depends: [
   "x509" {>= "1.0.2"}
   "base64" {>= "3.1.0"}
   "cbor" {>= "0.5"}
-  "ohex"
+  "ohex" {>= "0.2.0"}
 ]
 
 conflicts: [