diff --git a/src/dune_rules/ctypes/ctypes_field.ml b/src/dune_rules/ctypes/ctypes_field.ml
index 0bfbdcae1cd..2c4960f9b83 100644
--- a/src/dune_rules/ctypes/ctypes_field.ml
+++ b/src/dune_rules/ctypes/ctypes_field.ml
@@ -158,44 +158,48 @@ include Stanza.Make (struct
 let decode =
   let open Dune_lang.Decoder in
   fields
-    (let+ external_library_name = field "external_library_name" string
-     and+ build_flags_resolver =
-       field_o "build_flags_resolver" Build_flags_resolver.decode
-     and+ type_description = field "type_description" Type_description.decode
-     and+ loc_fd, function_description =
-       located (multi_field "function_description" Function_description.decode)
-     and+ headers = field_o "headers" Headers.decode
-     and+ generated_types = field_o "generated_types" Module_name.decode
-     and+ generated_entry_point = field "generated_entry_point" Module_name.decode
-     and+ deps = field_o "deps" (repeat Dep_conf.decode)
-     and+ version = Syntax.get_exn syntax in
-     let external_library_name = External_lib_name.of_string external_library_name in
-     (match
-        String.Map.of_list_map function_description ~f:(fun fd ->
-          let key = c_generated_functions_cout_c_of_lib ~external_library_name fd in
-          key, ())
-      with
-      | Ok _ -> ()
-      | Error (_, a, _) ->
-        User_error.raise
-          ~loc:loc_fd
-          [ Pp.textf
-              "Only a single (function_description) can instantiate %s as %s."
-              (Module_name.to_string a.functor_)
-              (Module_name.to_string a.instance)
-          ]);
-     { external_library_name
-     ; build_flags_resolver =
-         Option.value build_flags_resolver ~default:Build_flags_resolver.default
-     ; headers = Option.value headers ~default:Headers.default
-     ; type_description
-     ; function_description
-     ; generated_types =
-         Option.value generated_types ~default:(Module_name.of_string "Types_generated")
-     ; generated_entry_point
-     ; deps = Option.value ~default:[] deps
-     ; version
-     })
+    (let* deps = field "deps" (Bindings.decode Dep_conf.decode) ~default:Bindings.empty in
+     String_with_vars.add_user_vars_to_decoding_env
+       (Bindings.var_names deps)
+       (let+ external_library_name = field "external_library_name" string
+        and+ build_flags_resolver =
+          field_o "build_flags_resolver" Build_flags_resolver.decode
+        and+ type_description = field "type_description" Type_description.decode
+        and+ loc_fd, function_description =
+          located (multi_field "function_description" Function_description.decode)
+        and+ headers = field_o "headers" Headers.decode
+        and+ generated_types = field_o "generated_types" Module_name.decode
+        and+ generated_entry_point = field "generated_entry_point" Module_name.decode
+        and+ version = Syntax.get_exn syntax in
+        let external_library_name = External_lib_name.of_string external_library_name in
+        (match
+           String.Map.of_list_map function_description ~f:(fun fd ->
+             let key = c_generated_functions_cout_c_of_lib ~external_library_name fd in
+             key, ())
+         with
+         | Ok _ -> ()
+         | Error (_, a, _) ->
+           User_error.raise
+             ~loc:loc_fd
+             [ Pp.textf
+                 "Only a single (function_description) can instantiate %s as %s."
+                 (Module_name.to_string a.functor_)
+                 (Module_name.to_string a.instance)
+             ]);
+        { external_library_name
+        ; build_flags_resolver =
+            Option.value build_flags_resolver ~default:Build_flags_resolver.default
+        ; headers = Option.value headers ~default:Headers.default
+        ; type_description
+        ; function_description
+        ; generated_types =
+            Option.value
+              generated_types
+              ~default:(Module_name.of_string "Types_generated")
+        ; generated_entry_point
+        ; deps = Bindings.to_list deps
+        ; version
+        }))
 ;;
 
 let () =
diff --git a/test/blackbox-tests/test-cases/ctypes/deps-full-spec.t/bar.h b/test/blackbox-tests/test-cases/ctypes/deps-full-spec.t/bar.h
new file mode 100644
index 00000000000..8508c9d9481
--- /dev/null
+++ b/test/blackbox-tests/test-cases/ctypes/deps-full-spec.t/bar.h
@@ -0,0 +1 @@
+#define BAR_VERSION 1
diff --git a/test/blackbox-tests/test-cases/ctypes/deps-full-spec.t/baz.h b/test/blackbox-tests/test-cases/ctypes/deps-full-spec.t/baz.h
new file mode 100644
index 00000000000..04d503787d5
--- /dev/null
+++ b/test/blackbox-tests/test-cases/ctypes/deps-full-spec.t/baz.h
@@ -0,0 +1 @@
+#define BAZ_VERSION 1
diff --git a/test/blackbox-tests/test-cases/ctypes/deps-full-spec.t/dune b/test/blackbox-tests/test-cases/ctypes/deps-full-spec.t/dune
new file mode 100644
index 00000000000..5c7407000f0
--- /dev/null
+++ b/test/blackbox-tests/test-cases/ctypes/deps-full-spec.t/dune
@@ -0,0 +1,21 @@
+(executable
+ (name example)
+ (flags
+  (:standard -w -9-27))
+ (ctypes
+  (external_library_name libexample)
+  (build_flags_resolver pkg_config)
+  (deps
+   (:foo_h "foo.h")
+   (:bar_h bar.h)
+   baz.h)
+  (headers
+   (preamble
+    "#include <example.h>\n#include \"%{foo_h}\"\n#include \"%{bar_h}\"\n#include \"baz.h\"\n#include \"%{dep:qux.h}\""))
+  (type_description
+   (instance Types)
+   (functor Type_description))
+  (function_description
+   (instance Functions)
+   (functor Function_description))
+  (generated_entry_point C)))
diff --git a/test/blackbox-tests/test-cases/ctypes/deps-full-spec.t/dune-project b/test/blackbox-tests/test-cases/ctypes/deps-full-spec.t/dune-project
new file mode 100644
index 00000000000..1e9b8cc3eeb
--- /dev/null
+++ b/test/blackbox-tests/test-cases/ctypes/deps-full-spec.t/dune-project
@@ -0,0 +1,5 @@
+(lang dune 3.8)
+
+(using ctypes 0.3)
+
+(use_standard_c_and_cxx_flags false)
diff --git a/test/blackbox-tests/test-cases/ctypes/deps-full-spec.t/example.ml b/test/blackbox-tests/test-cases/ctypes/deps-full-spec.t/example.ml
new file mode 100644
index 00000000000..75fa327f298
--- /dev/null
+++ b/test/blackbox-tests/test-cases/ctypes/deps-full-spec.t/example.ml
@@ -0,0 +1,6 @@
+let () =
+  Printf.printf "%d\n" (C.Functions.add2 C.Types.foo_version);
+  Printf.printf "%d\n" (C.Functions.add2 C.Types.bar_version);
+  Printf.printf "%d\n" (C.Functions.add2 C.Types.baz_version);
+  Printf.printf "%d\n" (C.Functions.add2 C.Types.qux_version);
+  ()
diff --git a/test/blackbox-tests/test-cases/ctypes/deps-full-spec.t/foo.h b/test/blackbox-tests/test-cases/ctypes/deps-full-spec.t/foo.h
new file mode 100644
index 00000000000..b6083666e87
--- /dev/null
+++ b/test/blackbox-tests/test-cases/ctypes/deps-full-spec.t/foo.h
@@ -0,0 +1 @@
+#define FOO_VERSION 1
diff --git a/test/blackbox-tests/test-cases/ctypes/deps-full-spec.t/function_description.ml b/test/blackbox-tests/test-cases/ctypes/deps-full-spec.t/function_description.ml
new file mode 100644
index 00000000000..05c43d79e2f
--- /dev/null
+++ b/test/blackbox-tests/test-cases/ctypes/deps-full-spec.t/function_description.ml
@@ -0,0 +1,8 @@
+open Ctypes
+
+module Types = Types_generated
+
+module Functions (F : Ctypes.FOREIGN) = struct
+  open F
+  let add2 = foreign "example_add2" (int @-> returning int)
+end
diff --git a/test/blackbox-tests/test-cases/ctypes/deps-full-spec.t/qux.h b/test/blackbox-tests/test-cases/ctypes/deps-full-spec.t/qux.h
new file mode 100644
index 00000000000..74cdee31332
--- /dev/null
+++ b/test/blackbox-tests/test-cases/ctypes/deps-full-spec.t/qux.h
@@ -0,0 +1 @@
+#define QUX_VERSION 1
diff --git a/test/blackbox-tests/test-cases/ctypes/deps-full-spec.t/run.t b/test/blackbox-tests/test-cases/ctypes/deps-full-spec.t/run.t
new file mode 100644
index 00000000000..7679883a3cf
--- /dev/null
+++ b/test/blackbox-tests/test-cases/ctypes/deps-full-spec.t/run.t
@@ -0,0 +1,18 @@
+Build an example library as a DLL and set up the environment so that it looks
+like a system/distro library that can be probed with pkg-config and dynamically
+loaded.
+
+Then generate cstubs for it, build an executable that uses those cstubs, and
+run the executable that tests the library through the cstubs.
+
+  $ LIBEX=$(realpath "$PWD/../libexample")
+  $ DYLD_LIBRARY_PATH="$LIBEX" LD_LIBRARY_PATH="$LIBEX" PKG_CONFIG_PATH="$LIBEX/pkgconfig" PKG_CONFIG_ARGN="--define-prefix" dune exec ./example.exe
+  File "dune", line 14, characters 38-46:
+  14 |     "#include <example.h>\n#include \"%{foo_h}\"\n#include \"%{bar_h}\"\n#include \"baz.h\"\n#include \"%{dep:qux.h}\""))
+                                             ^^^^^^^^
+  Error: %{foo_h} isn't allowed in this position.
+  File "dune", line 14, characters 61-69:
+  14 |     "#include <example.h>\n#include \"%{foo_h}\"\n#include \"%{bar_h}\"\n#include \"baz.h\"\n#include \"%{dep:qux.h}\""))
+                                                                    ^^^^^^^^
+  Error: %{bar_h} isn't allowed in this position.
+  [1]
diff --git a/test/blackbox-tests/test-cases/ctypes/deps-full-spec.t/type_description.ml b/test/blackbox-tests/test-cases/ctypes/deps-full-spec.t/type_description.ml
new file mode 100644
index 00000000000..96e2916ea0a
--- /dev/null
+++ b/test/blackbox-tests/test-cases/ctypes/deps-full-spec.t/type_description.ml
@@ -0,0 +1,9 @@
+module Types (F : Ctypes.TYPE) = struct
+  open F
+
+  let foo_version = constant "FOO_VERSION" int
+  let bar_version = constant "BAR_VERSION" int
+  let baz_version = constant "BAZ_VERSION" int
+  let qux_version = constant "QUX_VERSION" int
+
+end