diff --git a/pkgs/development/ocaml-modules/mldoc/default.nix b/pkgs/development/ocaml-modules/mldoc/default.nix
index 7960042ff9cc..7a7e83d3c656 100644
--- a/pkgs/development/ocaml-modules/mldoc/default.nix
+++ b/pkgs/development/ocaml-modules/mldoc/default.nix
@@ -29,7 +29,7 @@ let
 in
 buildDunePackage rec {
   pname = "mldoc";
-  version = "1.5.2";
+  version = "1.5.6";
 
   minimalOCamlVersion = "4.10";
 
@@ -38,8 +38,8 @@ buildDunePackage rec {
   src = fetchFromGitHub {
     owner = "logseq";
     repo = "mldoc";
-    rev = "v${version}";
-    hash = "sha256-FiBlgTTGL5TQkbhpkOCKtBgDDxDs4S88Ps+XAHcNsJ4=";
+    rev = "2a700b2e4797e47505f423fd47dc07372bd7b04e"; # version not tagged
+    hash = "sha256-OS06fb/Nz8grztFEVwWiqsQQt2PQjqcgQFxQuAEYC54=";
   };
 
   buildInputs = [