diff --git a/src/lib_base/s.ml b/src/lib_base/s.ml
index aa0a01c39..e76664349 100644
--- a/src/lib_base/s.ml
+++ b/src/lib_base/s.ml
@@ -80,8 +80,6 @@ module type INTERNAL_HASH = sig
 
   include Tezos_crypto.S.HASH
 
-  val zero: t
-
   val of_b58check: string -> t tzresult
   val of_bytes: MBytes.t -> t tzresult
 
diff --git a/src/lib_crypto/blake2B.ml b/src/lib_crypto/blake2B.ml
index ebdcee2de..19eebf91b 100644
--- a/src/lib_crypto/blake2B.ml
+++ b/src/lib_crypto/blake2B.ml
@@ -107,6 +107,11 @@ module Make_minimal (K : Name) = struct
     and p6 = if len > 10 then String.sub p 10 (len - 10) else "" in
     [ p1 ; p2 ; p3 ; p4 ; p5 ; p6 ]
 
+  let zero =
+    match of_hex (String.make (size * 2) '0') with
+    | Some c -> c
+    | None -> assert false
+
 end
 
 module Make (R : sig
@@ -121,11 +126,6 @@ module Make (R : sig
 
   include Make_minimal(K)
 
-  let zero =
-    match of_hex (String.make (size * 2) '0') with
-    | Some c -> c
-    | None -> assert false
-
   (* Serializers *)
 
   type Base58.data += Hash of t
diff --git a/src/lib_crypto/s.ml b/src/lib_crypto/s.ml
index 35310ceae..04ed704f3 100644
--- a/src/lib_crypto/s.ml
+++ b/src/lib_crypto/s.ml
@@ -51,14 +51,14 @@ module type MINIMAL_HASH = sig
   val prefix_path: string -> string list
   val path_length: int
 
+  val zero: t
+
 end
 
 module type HASH = sig
 
   include MINIMAL_HASH
 
-  val zero: t
-
   val to_b58check: t -> string
   val to_short_b58check: t -> string
 
diff --git a/src/lib_protocol_environment_sigs/v1/s.mli b/src/lib_protocol_environment_sigs/v1/s.mli
index 6d8c5d40d..1f8eae26b 100644
--- a/src/lib_protocol_environment_sigs/v1/s.mli
+++ b/src/lib_protocol_environment_sigs/v1/s.mli
@@ -88,6 +88,8 @@ module type MINIMAL_HASH = sig
   val prefix_path: string -> string list
   val path_length: int
 
+  val zero: t
+
 end
 
 module type HASH = sig