diff --git a/mirage-crypto-ec.opam b/mirage-crypto-ec.opam
index d74cba51..6efd150e 100644
--- a/mirage-crypto-ec.opam
+++ b/mirage-crypto-ec.opam
@@ -37,6 +37,7 @@ depends: [
   "ppx_deriving" {with-test}
   "yojson" {with-test & >= "1.6.0"}
   "asn1-combinators" {with-test & >= "0.3.1"}
+  "ohex" {with-test & >= "0.2.0"}
 ]
 conflicts: [
   "ocaml-freestanding"
diff --git a/mirage-crypto-pk.opam b/mirage-crypto-pk.opam
index f5c6db71..39b11126 100644
--- a/mirage-crypto-pk.opam
+++ b/mirage-crypto-pk.opam
@@ -18,6 +18,7 @@ depends: [
   "dune" {>= "2.7"}
   "ounit2" {with-test}
   "randomconv" {with-test & >= "0.2.0"}
+  "ohex" {with-test & >= "0.2.0"}
   "mirage-crypto" {=version}
   "mirage-crypto-rng" {=version}
   "digestif" {>= "1.2.0"}