diff --git a/Admin/setup b/Admin/setup
--- a/Admin/setup
+++ b/Admin/setup
@@ -1,145 +1,150 @@
 #!/usr/bin/env bash
 #
 # Author: Makarius
 #
 # DESCRIPTION: setup for Isabelle repository clone or repository archive
 
 
 ## environment
 
 export ISABELLE_HOME="$(cd "$(dirname "$0")"; cd "$(pwd -P)"; cd ..; pwd)"
 
 ISABELLE_REPOS="https://isabelle.sketis.net/repos/isabelle"
 
 
 ## diagnostics
 
 function usage()
 {
   echo
   echo "Usage: Admin/setup [OPTIONS]"
   echo
   echo "  Options are:"
-  echo "    -C           enforce clean update of working directory (no backup!)"
+  echo "    -C           force clean working directory (no backup!)"
   echo "    -R           version is current official release"
   echo "    -U URL       Isabelle repository server (default: \"$ISABELLE_REPOS\")"
   echo "    -V PATH      version from explicit file or directory (file \"ISABELLE_VERSION\")"
+  echo "    -c           check clean working directory"
   echo "    -r REV       version according to Mercurial notation"
   echo "    -u           version is remote tip"
   echo
   echo "  Setup the current ISABELLE_HOME directory, which needs to be a"
   echo "  repository clone (all versions) or repository archive (fixed version)."
   echo
   exit 1
 }
 
 function fail()
 {
   echo "$1" >&2
   exit 2
 }
 
 
 ## process command line
 
 #options
 
-CLEAN=""
+CLEAN_FORCE=""
+CLEAN_CHECK=""
 
 VERSION=""
 VERSION_RELEASE=""
 VERSION_PATH=""
 VERSION_REV=""
 
-while getopts "CRU:V:r:u" OPT
+while getopts "CRU:V:cr:u" OPT
 do
   case "$OPT" in
     C)
-      CLEAN="--clean"
+      CLEAN_FORCE="--clean"
       ;;
     R)
       VERSION="true"
       VERSION_RELEASE="true"
       VERSION_PATH=""
       VERSION_REV=""
       ;;
     U)
       ISABELLE_REPOS="$OPTARG"
       ;;
     V)
       VERSION="true"
       VERSION_RELEASE=""
       VERSION_PATH="$OPTARG"
       VERSION_REV=""
       ;;
+    c)
+      CLEAN_CHECK="--check"
+      ;;
     r)
       VERSION="true"
       VERSION_RELEASE=""
       VERSION_PATH=""
       VERSION_REV="$OPTARG"
       ;;
     u)
       VERSION="true"
       VERSION_RELEASE=""
       VERSION_PATH=""
       VERSION_REV="tip"
       ;;
     \?)
       usage
       ;;
   esac
 done
 
 shift $(($OPTIND - 1))
 
 
 # args
 
 [ "$#" -ne 0 ] && usage
 
 
 ## main
 
 if [ -z "$VERSION" ]; then
   "$ISABELLE_HOME/bin/isabelle" components -I && \
   "$ISABELLE_HOME/bin/isabelle" components -a
 elif [ ! -d "$ISABELLE_HOME/.hg" ]; then
   fail "Not a repository clone: cannot specify version"
 else
   if [ -n "$VERSION_REV" ]; then
     REV="$VERSION_REV"
   elif [ -n "$VERSION_RELEASE" ]; then
     URL="$ISABELLE_REPOS/raw-file/tip/Admin/Release/official"
     REV="$(curl -s -f "$URL" | head -n1)"
     [ -z "$REV" ] && fail "Failed to access \"$URL\""
   elif [ -f "$VERSION_PATH" ]; then
     REV="$(cat "$VERSION_PATH")"
   elif [ -d "$VERSION_PATH" ]; then
     if [ -f "$VERSION_PATH/ISABELLE_VERSION" ]; then
       REV="$(cat "$VERSION_PATH/ISABELLE_VERSION")"
     else
       fail "Missing file \"$VERSION_PATH/ISABELLE_VERSION\""
     fi
   else
     fail "Missing file \"$VERSION_PATH\""
   fi
 
   export LANG=C
   export HGPLAIN=
 
   "$ISABELLE_HOME/bin/isabelle" components -I || exit "$?"
 
   #Atomic exec: avoid inplace update of running script!
   export CLEAN REV ISABELLE_REPOS
   exec bash -c '
     set -e
     "${HG:-hg}" -R "$ISABELLE_HOME" pull -r "$REV" "$ISABELLE_REPOS"
-    "${HG:-hg}" -R "$ISABELLE_HOME" update -r "$REV" $CLEAN
+    "${HG:-hg}" -R "$ISABELLE_HOME" update -r "$REV" $CLEAN_FORCE $CLEAN_CHECK
     "$ISABELLE_HOME/bin/isabelle" components -a
     "${HG:-hg}" -R "$ISABELLE_HOME" log -r "$REV"
     if [ ! -f "$ISABELLE_HOME/Admin/setup" ]; then
       echo >&2 "### The Admin/setup script has disappeared in this version"
       echo >&2 "### (need to invoke \"${HG:-hg} update\" before using it again)"
     fi
   '
 fi