diff --git a/src/dune_rules/expander.ml b/src/dune_rules/expander.ml
index d026505a405..d05e57eb3f2 100644
--- a/src/dune_rules/expander.ml
+++ b/src/dune_rules/expander.ml
@@ -529,16 +529,52 @@ let expand_pform_gen ~(context : Context.t) ~bindings ~dir ~source
                let p =
                  let open Memo.Build.O in
                  Resolve.Build.peek p >>| function
-                 | Ok p ->
-                   if
-                     (not lib_exec) || (not Sys.win32)
-                     || Filename.extension s = ".exe"
-                   then
-                     dep p
-                   else
-                     let p_exe = Path.extend_basename p ~suffix:".exe" in
-                     Action_builder.if_file_exists p_exe ~then_:(dep p_exe)
-                       ~else_:(dep p)
+                 | Ok p -> (
+                   match file with
+                   | ""
+                   | "." ->
+                     let lang_version =
+                       Dune_project.dune_version (Scope.project t.scope)
+                     in
+                     if lang_version < (3, 0) then
+                       Action_builder.return [ Value.Path p ]
+                     else
+                       User_error.raise
+                         ~loc:(Dune_lang.Template.Pform.loc source)
+                         [ Pp.textf
+                             "The form %%{%s:<libname>:%s} is no longer \
+                              supported since version 3.0 of the Dune \
+                              language."
+                             (if lib_private then
+                               "lib-private"
+                             else
+                               "lib")
+                             file
+                         ]
+                         ~hints:
+                           [ (match Lib_name.to_string lib with
+                             | "ctypes" ->
+                               Pp.text
+                                 "Did you know that Dune 3.0 supports ctypes \
+                                  natively? See the manual for more details."
+                             | _ ->
+                               Pp.textf
+                                 "If you are trying to use this form to refer \
+                                  to include a directory, you should instead \
+                                  use (foreign_stubs (include_dirs (lib %s))). \
+                                  See the manual for more details."
+                                 (Lib_name.to_string lib))
+                           ]
+                   | _ ->
+                     if
+                       (not lib_exec) || (not Sys.win32)
+                       || Filename.extension s = ".exe"
+                     then
+                       dep p
+                     else
+                       let p_exe = Path.extend_basename p ~suffix:".exe" in
+                       Action_builder.if_file_exists p_exe ~then_:(dep p_exe)
+                         ~else_:(dep p))
                  | Error () ->
                    let p =
                      if lib_private then
diff --git a/test/blackbox-tests/test-cases/github5264.t b/test/blackbox-tests/test-cases/github5264.t
index 0741875917d..df00ed1265c 100644
--- a/test/blackbox-tests/test-cases/github5264.t
+++ b/test/blackbox-tests/test-cases/github5264.t
@@ -9,40 +9,43 @@ syntax in lang Dune < 3.0.
 
   $ cat > dune <<'EOF'
   > (library (name ctypes))
+  > (library (name other))
   > (rule
   >  (alias a)
-  >  (action (run echo %{lib:ctypes:})))
+  >  (action (run echo %{lib-private:ctypes:})))
   > (rule
   >  (alias b)
-  >  (action (run echo %{lib:ctypes:})))
+  >  (action (run echo %{lib-private:other:.})))
   > EOF
 
-At the moment, we get a bad error with all language versions:
+We still support it with older version of the language, for backward
+compatibility purposes:
 
   $ echo '(lang dune 2.9)' > dune-project
   $ dune build @a
-  Error: File unavailable: /home/dim/.opam/4.13.1/lib/ctypes
-  This is not a regular file (S_DIR)
-  -> required by %{lib:ctypes:} at dune:4
-  -> required by alias a in dune:2
-  [1]
+  .
   $ dune build @b
-  Error: File unavailable: /home/dim/.opam/4.13.1/lib/ctypes
-  This is not a regular file (S_DIR)
-  -> required by %{lib:ctypes:} at dune:7
-  -> required by alias b in dune:5
-  [1]
+  .
+
+But we are more strict since 3.0:
 
   $ echo '(lang dune 3.0)' > dune-project
   $ dune build @a
-  Error: File unavailable: /home/dim/.opam/4.13.1/lib/ctypes
-  This is not a regular file (S_DIR)
-  -> required by %{lib:ctypes:} at dune:4
-  -> required by alias a in dune:2
+  File "dune", line 5, characters 19-41:
+  5 |  (action (run echo %{lib-private:ctypes:})))
+                         ^^^^^^^^^^^^^^^^^^^^^^
+  Error: The form %{lib-private:<libname>:} is no longer supported since
+  version 3.0 of the Dune language.
+  Hint: Did you know that Dune 3.0 supports ctypes natively? See the manual for
+  more details.
   [1]
   $ dune build @b
-  Error: File unavailable: /home/dim/.opam/4.13.1/lib/ctypes
-  This is not a regular file (S_DIR)
-  -> required by %{lib:ctypes:} at dune:7
-  -> required by alias b in dune:5
+  File "dune", line 8, characters 19-41:
+  8 |  (action (run echo %{lib-private:other:.})))
+                         ^^^^^^^^^^^^^^^^^^^^^^
+  Error: The form %{lib-private:<libname>:.} is no longer supported since
+  version 3.0 of the Dune language.
+  Hint: If you are trying to use this form to refer to an include directory,
+  you should instead use (foreign_stubs (include_dirs (lib other))). See the
+  manual for more details.
   [1]