diff --git a/pkgs/development/ocaml-modules/optcomp/default.nix b/pkgs/development/ocaml-modules/optcomp/default.nix
index 7afbf3a4b407..8953373954a5 100644
--- a/pkgs/development/ocaml-modules/optcomp/default.nix
+++ b/pkgs/development/ocaml-modules/optcomp/default.nix
@@ -4,8 +4,8 @@ stdenv.mkDerivation {
   name = "ocaml-optcomp-1.6";
   src = fetchurl {
     url = https://github.com/diml/optcomp/archive/1.6.tar.gz;
-    md5 = "d3587244dba1b8b10f24d0b60a8c700d";
-    };
+    sha256 = "0hhhb2gisah1h22zlg5iszbgqxdd7x85cwd57bd4mfkx9l7dh8jh";
+  };
   
   createFindlibDestdir = true;