diff --git a/src/lib_shell/block_directory.ml b/src/lib_shell/block_directory.ml
index 6009c3df0..66f1cad51 100644
--- a/src/lib_shell/block_directory.ml
+++ b/src/lib_shell/block_directory.ml
@@ -166,7 +166,7 @@ let build_raw_rpc_directory
   register1 S.Context.read begin fun block path q () ->
     let depth = Option.unopt ~default:max_int q#depth in
     fail_unless (depth >= 0)
-      (Tezos_shell_services.Block_services.Invalid_depth_arg (path, depth)) >>=? fun () ->
+      (Tezos_shell_services.Block_services.Invalid_depth_arg depth) >>=? fun () ->
     State.Block.context block >>= fun context ->
     Context.mem context path >>= fun mem ->
     Context.dir_mem context path >>= fun dir_mem ->
diff --git a/src/lib_shell_services/block_services.ml b/src/lib_shell_services/block_services.ml
index 4288f6b87..24f771bb8 100644
--- a/src/lib_shell_services/block_services.ml
+++ b/src/lib_shell_services/block_services.ml
@@ -126,19 +126,19 @@ let raw_context_encoding =
        ])
 
 type error +=
-  | Invalid_depth_arg of (string list * int)
+  | Invalid_depth_arg of int
 
 let () =
   register_error_kind
     `Permanent
-    ~id:"raw_context.missing_key"
-    ~title:"...FIXME..."
-    ~description:"...FIXME..."
-    ~pp:(fun ppf path ->
-        Format.fprintf ppf "Missing key: %s" (String.concat "/" path))
-    Data_encoding.(obj1 (req "path" (list string)))
-    (function Missing_key path -> Some path | _ -> None)
-    (fun path -> Missing_key path)
+    ~id:"raw_context.invalid_depth"
+    ~title:"Invalid depth argument"
+    ~description:"The raw context extraction depth argument must be positive."
+    ~pp:(fun ppf depth ->
+        Format.fprintf ppf "Extraction depth %d is invalid" depth)
+    Data_encoding.(obj1 (req "depth" int31))
+    (function Invalid_depth_arg depth -> Some depth | _ -> None)
+    (fun depth -> Invalid_depth_arg depth)
 
 module type PROTO = sig
   val hash: Protocol_hash.t
diff --git a/src/lib_shell_services/block_services.mli b/src/lib_shell_services/block_services.mli
index e7302e2ee..e60493245 100644
--- a/src/lib_shell_services/block_services.mli
+++ b/src/lib_shell_services/block_services.mli
@@ -46,7 +46,7 @@ type raw_context =
 val pp_raw_context: Format.formatter -> raw_context -> unit
 
 type error +=
-  | Invalid_depth_arg of (string list * int)
+  | Invalid_depth_arg of int
 
 module type PROTO = sig
   val hash: Protocol_hash.t