diff --git a/pkgs/data/sgml+xml/schemas/sgml-dtd/docbook/4.1.nix b/pkgs/data/sgml+xml/schemas/sgml-dtd/docbook/4.1.nix
index 4a106db44057..d20313d7e237 100644
--- a/pkgs/data/sgml+xml/schemas/sgml-dtd/docbook/4.1.nix
+++ b/pkgs/data/sgml+xml/schemas/sgml-dtd/docbook/4.1.nix
@@ -13,7 +13,7 @@ let
   };
 
   isoents = fetchurl {
-    url = "http://www.oasis-open.org/cover/ISOEnts.zip";
+    url = "https://web.archive.org/web/20250220122223/http://xml.coverpages.org/ISOEnts.zip";
     sha256 = "1clrkaqnvc1ja4lj8blr0rdlphngkcda3snm7b9jzvcn76d3br6w";
   };