diff --git a/pkgs/development/ocaml-modules/bistro/default.nix b/pkgs/development/ocaml-modules/bistro/default.nix
index 192bb470a66d..8f84a973bf0f 100644
--- a/pkgs/development/ocaml-modules/bistro/default.nix
+++ b/pkgs/development/ocaml-modules/bistro/default.nix
@@ -7,7 +7,7 @@
 , bos
 , core
 , core_kernel
-, core_unix
+, core_unix ? null
 , lwt_react
 , ocamlgraph
 , ppx_sexp_conv
diff --git a/pkgs/development/ocaml-modules/bls12-381/default.nix b/pkgs/development/ocaml-modules/bls12-381/default.nix
index 8330ce3e2bc3..20b2cd66a758 100644
--- a/pkgs/development/ocaml-modules/bls12-381/default.nix
+++ b/pkgs/development/ocaml-modules/bls12-381/default.nix
@@ -1,5 +1,8 @@
 { lib, buildDunePackage, fetchFromGitLab
-, ff-sig, zarith, zarith_stubs_js, integers_stubs_js, integers, hex
+, ff-sig, zarith
+, zarith_stubs_js ? null
+, integers_stubs_js
+, integers, hex
 , alcotest, ff-pbt
 }:
 
diff --git a/pkgs/development/ocaml-modules/cohttp/async.nix b/pkgs/development/ocaml-modules/cohttp/async.nix
index 3e6ac4ae2d96..3236d4775070 100644
--- a/pkgs/development/ocaml-modules/cohttp/async.nix
+++ b/pkgs/development/ocaml-modules/cohttp/async.nix
@@ -7,7 +7,7 @@
 , async_unix
 , cohttp
 , conduit-async
-, core_unix
+, core_unix ? null
 , uri
 , uri-sexp
 , logs
diff --git a/pkgs/development/ocaml-modules/data-encoding/default.nix b/pkgs/development/ocaml-modules/data-encoding/default.nix
index 5a17abdcc532..2b4013eb46a0 100644
--- a/pkgs/development/ocaml-modules/data-encoding/default.nix
+++ b/pkgs/development/ocaml-modules/data-encoding/default.nix
@@ -5,7 +5,7 @@
 , either
 , ezjsonm
 , zarith
-, zarith_stubs_js
+, zarith_stubs_js ? null
 , hex
 , json-data-encoding
 , json-data-encoding-bson
diff --git a/pkgs/development/ocaml-modules/faraday/async.nix b/pkgs/development/ocaml-modules/faraday/async.nix
index 90f56c159632..f24866a815c1 100644
--- a/pkgs/development/ocaml-modules/faraday/async.nix
+++ b/pkgs/development/ocaml-modules/faraday/async.nix
@@ -1,4 +1,4 @@
-{ buildDunePackage, lib, faraday, core_unix, async }:
+{ buildDunePackage, lib, faraday, core_unix ? null, async }:
 
 buildDunePackage rec {
   pname = "faraday-async";
diff --git a/pkgs/development/ocaml-modules/hack_parallel/default.nix b/pkgs/development/ocaml-modules/hack_parallel/default.nix
index 8d1414731f13..afd49b871656 100644
--- a/pkgs/development/ocaml-modules/hack_parallel/default.nix
+++ b/pkgs/development/ocaml-modules/hack_parallel/default.nix
@@ -1,4 +1,4 @@
-{ lib, fetchFromGitHub, buildDunePackage, core, core_unix, pkg-config
+{ lib, fetchFromGitHub, buildDunePackage, core, core_unix ? null, pkg-config
 , sqlite }:
 buildDunePackage rec {
   pname = "hack_parallel";
diff --git a/pkgs/development/ocaml-modules/integers_stubs_js/default.nix b/pkgs/development/ocaml-modules/integers_stubs_js/default.nix
index fc06efae7e04..59d47d2daf5f 100644
--- a/pkgs/development/ocaml-modules/integers_stubs_js/default.nix
+++ b/pkgs/development/ocaml-modules/integers_stubs_js/default.nix
@@ -1,6 +1,6 @@
 {
   lib, fetchFromGitHub, buildDunePackage
-, zarith_stubs_js
+, zarith_stubs_js ? null
 }:
 
 buildDunePackage rec {
diff --git a/pkgs/development/ocaml-modules/magic-trace/default.nix b/pkgs/development/ocaml-modules/magic-trace/default.nix
index 1f1417f67275..39bdca1119a4 100644
--- a/pkgs/development/ocaml-modules/magic-trace/default.nix
+++ b/pkgs/development/ocaml-modules/magic-trace/default.nix
@@ -1,5 +1,5 @@
-{ lib, fetchFromGitHub, buildDunePackage, async, cohttp_static_handler
-, core_unix, owee, ppx_jane, shell }:
+{ lib, fetchFromGitHub, buildDunePackage, async, cohttp_static_handler ? null
+, core_unix ? null, owee, ppx_jane, shell ? null }:
 
 buildDunePackage rec {
   pname = "magic-trace";
diff --git a/pkgs/development/ocaml-modules/mldoc/default.nix b/pkgs/development/ocaml-modules/mldoc/default.nix
index 058261a78d3d..7960042ff9cc 100644
--- a/pkgs/development/ocaml-modules/mldoc/default.nix
+++ b/pkgs/development/ocaml-modules/mldoc/default.nix
@@ -6,7 +6,7 @@
 , cmdliner
 , core
 , core_bench
-, core_unix
+, core_unix ? null
 , js_of_ocaml
 , js_of_ocaml-ppx
 , ppx_deriving_yojson