diff --git a/src/scala/dof.scala b/src/scala/dof.scala
index 7e3fa26c..ea1bc5e5 100644
--- a/src/scala/dof.scala
+++ b/src/scala/dof.scala
@@ -33,6 +33,7 @@ package isabelle.dof
 
 object DOF {
   val isabelle_version = "2022"
+  val isabelle_url = "https://isabelle.in.tum.de/website-Isabelle2022"
 
   val version = "Unreleased"
     // Isabelle/DOF version: "Unreleased" for development, semantic version for releases
diff --git a/src/scala/dof_document_build.scala b/src/scala/dof_document_build.scala
index e1e66e12..3a763e10 100644
--- a/src/scala/dof_document_build.scala
+++ b/src/scala/dof_document_build.scala
@@ -83,7 +83,7 @@ object DOF_Document_Build
 
       // create dof-config.sty
       File.write(directory.doc_dir + Path.explode("dof-config.sty"), """
-\newcommand{\isabelleurl}{https://isabelle.in.tum.de/website-Isabelle2022/""" + DOF.isabelle_version + """}
+\newcommand{\isabelleurl}{""" + DOF.isabelle_url + """}
 \newcommand{\dofurl}{""" + DOF.url + """}
 \newcommand{\dof@isabelleversion}{""" + DOF.isabelle_version + """}
 \newcommand{\isabellefullversion}{""" + DOF.isabelle_version + """\xspace}