diff --git a/src/dune_rules/scope.ml b/src/dune_rules/scope.ml
index 91513dc4b6f5..de097e1a0b0f 100644
--- a/src/dune_rules/scope.ml
+++ b/src/dune_rules/scope.ml
@@ -441,6 +441,12 @@ module DB = struct
       | Deprecated_library_name { old_name = old_public_name, _; _ } ->
         Public_lib.name old_public_name
     ;;
+
+    let loc = function
+      | Library lib -> Lib.Local.to_lib lib |> Lib.info |> Lib_info.loc
+      | Deprecated_library_name { old_name = old_public_name, _; _ } ->
+        Public_lib.loc old_public_name
+    ;;
   end
 
   let lib_entries_of_package =
@@ -502,6 +508,39 @@ module DB = struct
     in
     fun (ctx : Context_name.t) pkg_name ->
       let+ map = per_context ctx in
-      Package.Name.Map.Multi.find map pkg_name
+      match Package.Name.Map.Multi.find map pkg_name with
+      | ([] | [ _ ]) as xs -> xs
+      | libs ->
+        let _by_name =
+          List.fold_left libs ~init:Lib_name.Map.empty ~f:(fun by_name entry2 ->
+            let public_name = Lib_entry.name entry2 in
+            Lib_name.Map.update by_name public_name ~f:(function
+              | None -> Some entry2
+              | Some entry1 ->
+                let loc1 = Lib_entry.loc entry1
+                and loc2 = Lib_entry.loc entry2 in
+                let main_message =
+                  Pp.textf
+                    "Public library %s is defined twice:"
+                    (Lib_name.to_string public_name)
+                in
+                let annots =
+                  let main = User_message.make ~loc:loc2 [ main_message ] in
+                  let related =
+                    [ User_message.make ~loc:loc1 [ Pp.text "Already defined here" ] ]
+                  in
+                  User_message.Annots.singleton
+                    Compound_user_error.annot
+                    [ Compound_user_error.make ~main ~related ]
+                in
+                User_error.raise
+                  ~annots
+                  ~loc:loc2
+                  [ main_message
+                  ; Pp.textf "- %s" (Loc.to_file_colon_line loc1)
+                  ; Pp.textf "- %s" (Loc.to_file_colon_line loc2)
+                  ]))
+        in
+        libs
   ;;
 end
diff --git a/test/blackbox-tests/test-cases/lib-collision/lib-collision-public-same-public-name-same-folder.t b/test/blackbox-tests/test-cases/lib-collision/lib-collision-public-same-public-name-same-folder.t
new file mode 100644
index 000000000000..b925fd7d492f
--- /dev/null
+++ b/test/blackbox-tests/test-cases/lib-collision/lib-collision-public-same-public-name-same-folder.t
@@ -0,0 +1,53 @@
+Public libraries using the same library name, in the same context, defined in
+the same folder.
+
+  $ mkdir -p a b
+
+  $ cat > dune-project << EOF
+  > (lang dune 3.13)
+  > (package (name bar) (allow_empty))
+  > EOF
+
+  $ cat > a/dune << EOF
+  > (library
+  >  (name foo)
+  >  (public_name bar.foo))
+  > (library
+  >  (name bar)
+  >  (public_name bar.foo))
+  > EOF
+
+Without any consumers of the libraries
+
+  $ dune build
+  File "a/dune", lines 1-3, characters 0-44:
+  1 | (library
+  2 |  (name foo)
+  3 |  (public_name bar.foo))
+  Error: Public library bar.foo is defined twice:
+  - a/dune:4
+  - a/dune:1
+  [1]
+
+With some consumer
+
+  $ cat > dune << EOF
+  > (executable
+  >  (name main)
+  >  (libraries foo))
+  > EOF
+
+  $ cat > main.ml <<EOF
+  > let () = Foo.x
+  > EOF
+
+  $ dune build
+  File "a/dune", lines 1-3, characters 0-44:
+  1 | (library
+  2 |  (name foo)
+  3 |  (public_name bar.foo))
+  Error: Public library bar.foo is defined twice:
+  - a/dune:4
+  - a/dune:1
+  [1]
+
diff --git a/test/blackbox-tests/test-cases/lib-collision/lib-collision-public-same-public-name.t b/test/blackbox-tests/test-cases/lib-collision/lib-collision-public-same-public-name.t
index 3ed2f14afeb1..c73066e69077 100644
--- a/test/blackbox-tests/test-cases/lib-collision/lib-collision-public-same-public-name.t
+++ b/test/blackbox-tests/test-cases/lib-collision/lib-collision-public-same-public-name.t
@@ -23,6 +23,14 @@ different folders.
 Without any consumers of the libraries
 
   $ dune build
+  File "b/dune", lines 1-3, characters 0-44:
+  1 | (library
+  2 |  (name bar)
+  3 |  (public_name bar.foo))
+  Error: Public library bar.foo is defined twice:
+  - a/dune:1
+  - b/dune:1
+  [1]
 
 With some consumer
 
@@ -37,11 +45,11 @@ With some consumer
   > EOF
 
   $ dune build
-  File "a/dune", lines 1-3, characters 0-44:
+  File "b/dune", lines 1-3, characters 0-44:
   1 | (library
-  2 |  (name foo)
+  2 |  (name bar)
   3 |  (public_name bar.foo))
-  Error: Library with name "bar.foo" is already defined in b/dune:1. Either
-  change one of the names, or enable them conditionally using the 'enabled_if'
-  field.
+  Error: Public library bar.foo is defined twice:
+  - a/dune:1
+  - b/dune:1
   [1]