diff --git a/src/dune_engine/action_exec.ml b/src/dune_engine/action_exec.ml
index 2159d838668..118e07247aa 100644
--- a/src/dune_engine/action_exec.ml
+++ b/src/dune_engine/action_exec.ml
@@ -65,7 +65,7 @@ module Dynamic_dep = struct
 end
 
 module Exec_result = struct
-  type t = { dynamic_deps_stages : (Dynamic_dep.Set.t * Dep.Facts.t) List.t }
+  type t = { dynamic_deps_stages : (Dep.Set.t * Dep.Facts.t) list }
 end
 
 type done_or_more_deps =
@@ -540,9 +540,8 @@ let exec_until_all_deps_ready ~display ~ectx ~eenv t =
     match result with
     | Done -> Fiber.return stages
     | Need_more_deps (relative_deps, deps_to_build) ->
-      let* fact_map =
-        ectx.build_deps (Dynamic_dep.Set.to_dep_set deps_to_build)
-      in
+      let deps_to_build = Dynamic_dep.Set.to_dep_set deps_to_build in
+      let* fact_map = ectx.build_deps deps_to_build in
       let stages = (deps_to_build, fact_map) :: stages in
       let eenv =
         { eenv with
diff --git a/src/dune_engine/action_exec.mli b/src/dune_engine/action_exec.mli
index 9d763692a64..d5ddb208f91 100644
--- a/src/dune_engine/action_exec.mli
+++ b/src/dune_engine/action_exec.mli
@@ -1,29 +1,12 @@
 open Import
 
-(** Type for dependency requested by the dynamic action.
-
-    Must be different from [Dep.t] type because we require it to be
-    marshallable. *)
-module Dynamic_dep : sig
-  type t =
-    | File of Path.t
-    | Glob of Path.t * Glob.t
-
-  val to_dep : t -> Dep.t
-
-  val compare : t -> t -> Ordering.t
-
-  module Map : Map.S with type key := t
-
-  module Set : sig
-    include Set.S with type elt = t and type 'a map = 'a Map.t
-
-    val to_dep_set : t -> Dep.Set.t
-  end
-end
-
 module Exec_result : sig
-  type t = { dynamic_deps_stages : (Dynamic_dep.Set.t * Dep.Facts.t) List.t }
+  type t =
+    { dynamic_deps_stages :
+        (* The set can be derived from the facts by getting the keys of the
+           facts map. We don't do it because conversion isn't free *)
+        (Dep.Set.t * Dep.Facts.t) list
+    }
 end
 
 type input =
diff --git a/src/dune_engine/rule_cache.ml b/src/dune_engine/rule_cache.ml
index 69178ec4d9a..68bedf3d624 100644
--- a/src/dune_engine/rule_cache.ml
+++ b/src/dune_engine/rule_cache.ml
@@ -14,7 +14,7 @@ module Workspace_local = struct
     module Entry = struct
       type t =
         { rule_digest : Digest.t
-        ; dynamic_deps_stages : (Action_exec.Dynamic_dep.Set.t * Digest.t) list
+        ; dynamic_deps_stages : (Dep.Set.t * Digest.t) list
         ; targets_digest : Digest.t
         }
 
@@ -23,7 +23,7 @@ module Workspace_local = struct
           [ ("rule_digest", Digest.to_dyn rule_digest)
           ; ( "dynamic_deps_stages"
             , Dyn.list
-                (Dyn.pair Action_exec.Dynamic_dep.Set.to_dyn Digest.to_dyn)
+                (Dyn.pair Dep.Set.to_dyn Digest.to_dyn)
                 dynamic_deps_stages )
           ; ("targets_digest", Digest.to_dyn targets_digest)
           ]
@@ -167,7 +167,6 @@ module Workspace_local = struct
         match stages with
         | [] -> Fiber.return (Result.Hit produced_targets)
         | (deps, old_digest) :: rest -> (
-          let deps = Action_exec.Dynamic_dep.Set.to_dep_set deps in
           let open Fiber.O in
           let* deps = Memo.run (build_deps deps) in
           let new_digest = Dep.Facts.digest deps ~env in
diff --git a/src/dune_engine/rule_cache.mli b/src/dune_engine/rule_cache.mli
index 132e3b30bcd..c0dc961cf18 100644
--- a/src/dune_engine/rule_cache.mli
+++ b/src/dune_engine/rule_cache.mli
@@ -25,7 +25,7 @@ module Workspace_local : sig
   val store :
        head_target:Path.Build.t
     -> rule_digest:Digest.t
-    -> dynamic_deps_stages:(Action_exec.Dynamic_dep.Set.t * Digest.t) list
+    -> dynamic_deps_stages:(Dep.Set.t * Digest.t) list
     -> targets_digest:Digest.t
     -> unit
 end