diff --git a/src/build_interpret.ml b/src/build_interpret.ml
index 32eacd3d..82c9f663 100644
--- a/src/build_interpret.ml
+++ b/src/build_interpret.ml
@@ -88,7 +88,7 @@ let static_deps t ~all_targets =
   loop (Build.repr t) { rule_deps = Pset.empty; action_deps = Pset.empty }
 
 let lib_deps =
-  let rec loop : type a b. (a, b) t -> Build.lib_deps option -> Build.lib_deps option
+  let rec loop : type a b. (a, b) t -> Build.lib_deps -> Build.lib_deps
     = fun t acc ->
       match t with
       | Arr _ -> acc
@@ -105,17 +105,13 @@ let lib_deps =
       | Dyn_paths t -> loop t acc
       | Contents _ -> acc
       | Lines_of _ -> acc
-      | Record_lib_deps deps ->
-        begin match acc with
-        | None -> Some deps
-        | Some acc -> Some (Build.merge_lib_deps deps acc)
-        end
+      | Record_lib_deps deps -> Build.merge_lib_deps deps acc
       | Fail _ -> acc
       | If_file_exists (_, state) ->
         loop (get_if_file_exists_exn state) acc
       | Memo m -> loop m.t acc
   in
-  fun t -> loop (Build.repr t) None
+  fun t -> loop (Build.repr t) String_map.empty
 
 let targets =
   let rec loop : type a b. (a, b) t -> Target.t list -> Target.t list = fun t acc ->
diff --git a/src/build_interpret.mli b/src/build_interpret.mli
index 07c09737..e8c439fe 100644
--- a/src/build_interpret.mli
+++ b/src/build_interpret.mli
@@ -47,7 +47,7 @@ val static_deps
 
 val lib_deps
   :  (_, _) Build.t
-  -> Build.lib_deps option
+  -> Build.lib_deps
 
 val targets
   :  (_, _) Build.t
diff --git a/src/build_system.ml b/src/build_system.ml
index bb74da44..cb69ad36 100644
--- a/src/build_system.ml
+++ b/src/build_system.ml
@@ -1165,7 +1165,7 @@ module Ir_set = Set.Make(Internal_rule)
 
 let rules_for_files t paths =
   List.filter_map paths ~f:(fun path ->
-    if Path.is_in_build_dir path then load_dir t ~dir:path;
+    if Path.is_in_build_dir path then load_dir t ~dir:(Path.parent path);
     match Hashtbl.find t.files path with
     | None -> None
     | Some (File_spec.T { rule; _ }) -> Some rule)
@@ -1207,29 +1207,28 @@ let all_lib_deps t ~request =
   let targets = static_deps_of_request t request in
   List.fold_left (rules_for_targets t targets) ~init:Pmap.empty
     ~f:(fun acc (rule : Internal_rule.t) ->
-      let lib_deps =
-        match Build_interpret.lib_deps rule.build with
-        | None -> Pmap.empty
-        | Some deps -> Pmap.singleton rule.dir deps in
-      Pmap.merge acc lib_deps ~f:(fun _ a b ->
-        match a, b with
-        | None, None -> None
-        | Some a, None -> Some a
-        | None, Some b -> Some b
-        | Some a, Some b -> Some (Build.merge_lib_deps a b)))
+      let deps = Build_interpret.lib_deps rule.build in
+      if String_map.is_empty deps then
+        acc
+      else
+        let deps =
+          match Pmap.find rule.dir acc with
+          | None -> deps
+          | Some deps' -> Build.merge_lib_deps deps deps'
+        in
+        Pmap.add acc ~key:rule.dir ~data:deps)
 
 let all_lib_deps_by_context t ~request =
   let targets = static_deps_of_request t request in
-  rules_for_targets t targets
-  |> List.fold_left  ~init:[] ~f:(fun acc (rule : Internal_rule.t) ->
-    let lib_deps =
-        match Build_interpret.lib_deps rule.build with
-        | None -> Pmap.empty
-        | Some deps -> Pmap.singleton rule.dir deps in
-    Path.Map.fold lib_deps ~init:acc ~f:(fun ~key:path ~data:lib_deps acc ->
-      match Path.extract_build_context path with
+  let rules = rules_for_targets t targets in
+  List.fold_left rules ~init:[] ~f:(fun acc (rule : Internal_rule.t) ->
+    let deps = Build_interpret.lib_deps rule.build in
+    if String_map.is_empty deps then
+      acc
+    else
+      match Path.extract_build_context rule.dir with
       | None -> acc
-      | Some (context, _) -> (context, lib_deps) :: acc))
+      | Some (context, _) -> (context, deps) :: acc)
   |> String_map.of_alist_multi
   |> String_map.map ~f:(function
     | [] -> String_map.empty
diff --git a/src/super_context.ml b/src/super_context.ml
index b939ad34..6197c215 100644
--- a/src/super_context.ml
+++ b/src/super_context.ml
@@ -303,7 +303,8 @@ module Libs = struct
     in
     let vrequires = vrequires t ~dir ~item in
     add_rule t
-      (Build.record_lib_deps ~kind:dep_kind (List.map virtual_deps ~f:Lib_dep.direct)
+      (Build.record_lib_deps ~kind:dep_kind
+         (List.map virtual_deps ~f:Lib_dep.direct)
        >>>
        Build.fanout
          (closure t ~scope ~dep_kind libraries)
diff --git a/test/blackbox-tests/test-cases/findlib/run.t b/test/blackbox-tests/test-cases/findlib/run.t
index 7baa061f..7ef53195 100644
--- a/test/blackbox-tests/test-cases/findlib/run.t
+++ b/test/blackbox-tests/test-cases/findlib/run.t
@@ -1 +1,5 @@
   $ $JBUILDER external-lib-deps --root . -j1 --display quiet @install
+  These are the external library dependencies in the default context:
+  - a
+  - b
+  - c