diff --git a/etc/settings b/etc/settings
--- a/etc/settings
+++ b/etc/settings
@@ -1,176 +1,176 @@
 # -*- shell-script -*- :mode=shellscript:
 #
 # Isabelle system settings.
 #
 # Important notes:
 #   * See the "system" manual for explanations on Isabelle settings
 #   * User settings go into $ISABELLE_HOME_USER/etc/settings
 #   * DO NOT EDIT the repository copy of this file!
 #   * DO NOT COPY this file into the $ISABELLE_HOME_USER directory!
 
 ###
 ### Isabelle/Scala
 ###
 
 ISABELLE_JAVA_SYSTEM_OPTIONS="-server -Dfile.encoding=UTF-8 -Disabelle.threads=0"
 
 ISABELLE_TOOL_JAVA_OPTIONS="-Djava.awt.headless=true -Xms512m -Xmx4g -Xss16m"
 
 ISABELLE_SCALAC_OPTIONS="-encoding UTF-8 -nowarn -target:jvm-1.8 -J-Xms512m -J-Xmx4g -J-Xss16m"
 
 classpath "$ISABELLE_HOME/lib/classes/Pure.jar"
 
 isabelle_scala_service 'isabelle.Tools'
 [ -d "$ISABELLE_HOME/Admin" ] && isabelle_scala_service 'isabelle.Admin_Tools'
 
 isabelle_scala_service 'isabelle.Scala_Functions'
 
 isabelle_scala_service 'isabelle.Sessions$File_Format'
 isabelle_scala_service 'isabelle.Bibtex$File_Format'
 
 isabelle_scala_service 'isabelle.ML_Statistics$Handler'
 isabelle_scala_service 'isabelle.Scala$Handler'
 isabelle_scala_service 'isabelle.Print_Operation$Handler'
 isabelle_scala_service 'isabelle.Simplifier_Trace$Handler'
 isabelle_scala_service 'isabelle.Server_Commands'
 
 #paranoia settings -- avoid intrusion of alien options
 unset "_JAVA_OPTIONS"
 unset "JAVA_TOOL_OPTIONS"
 
 #paranoia settings -- avoid problems of Java/Swing versus XIM/IBus etc.
 unset XMODIFIERS
 
 
 ###
 ### Interactive sessions (cf. isabelle console)
 ###
 
 ISABELLE_LINE_EDITOR="rlwrap"
 
 
 ###
 ### Batch sessions (cf. isabelle build)
 ###
 
 ISABELLE_BUILD_OPTIONS=""
 
 
 ###
 ### Document preparation (cf. isabelle latex/document)
 ###
 
 ISABELLE_PDFLATEX="lualatex --file-line-error"
 ISABELLE_BIBTEX="bibtex"
 ISABELLE_MAKEINDEX="makeindex"
 ISABELLE_EPSTOPDF="epstopdf"
 
 
 ###
 ### Misc path settings
 ###
 
 isabelle_directory '~'
 isabelle_directory '$ISABELLE_HOME_USER'
 isabelle_directory '~~'
 
 ISABELLE_COMPONENT_REPOSITORY="https://isabelle.sketis.net/components"
 ISABELLE_COMPONENTS_BASE="$USER_HOME/.isabelle/contrib"
 
 # The place for user configuration, heap files, etc.
 if [ -z "$ISABELLE_IDENTIFIER" ]; then
   ISABELLE_HOME_USER="$USER_HOME/.isabelle"
 else
   ISABELLE_HOME_USER="$USER_HOME/.isabelle/$ISABELLE_IDENTIFIER"
 fi
 
 # Where to look for isabelle tools (multiple dirs separated by ':').
 ISABELLE_TOOLS="$ISABELLE_HOME/lib/Tools"
 
 # Location for temporary files (should be on a local file system).
 ISABELLE_TMP_PREFIX="${TMPDIR:-/tmp}/isabelle-$USER"
 
 # Heap locations.
 ISABELLE_HEAPS="$ISABELLE_HOME_USER/heaps"
 ISABELLE_HEAPS_SYSTEM="$ISABELLE_HOME/heaps"
 
 # HTML browser info.
 ISABELLE_BROWSER_INFO="$ISABELLE_HOME_USER/browser_info"
 ISABELLE_BROWSER_INFO_SYSTEM="$ISABELLE_HOME/browser_info"
 
 # Site settings check -- just to make it a little bit harder to copy this file verbatim!
 [ -n "$ISABELLE_SITE_SETTINGS_PRESENT" ] && \
   { echo >&2 "### Isabelle site settings already present!  Maybe copied etc/settings in full?"; }
 ISABELLE_SITE_SETTINGS_PRESENT=true
 
 
 ###
 ### Default logic
 ###
 
 ISABELLE_LOGIC=HOL
 
 
 ###
 ### Docs
 ###
 
 # Where to look for docs (multiple dirs separated by ':').
 ISABELLE_DOCS="$ISABELLE_HOME/doc"
 
 ISABELLE_DOCS_RELEASE_NOTES="~~/ANNOUNCE:~~/README:~~/NEWS:~~/COPYRIGHT:~~/CONTRIBUTORS:~~/contrib/README:~~/src/Tools/jEdit/README:~~/README_REPOSITORY"
 ISABELLE_DOCS_EXAMPLES="~~/src/HOL/Examples/Seq.thy:~~/src/HOL/Examples/Drinker.thy:~~/src/HOL/Examples/ML.thy:~~/src/HOL/Unix/Unix.thy:~~/src/Tools/SML/Examples.thy:~~/src/Pure/ROOT.ML"
 
 # "open" within desktop environment (potentially asynchronous)
 case "$ISABELLE_PLATFORM_FAMILY" in
   linux)
     ISABELLE_OPEN="xdg-open"
     ;;
   macos)
     ISABELLE_OPEN="open"
     ;;
   windows)
     ISABELLE_OPEN="cygstart"
     ;;
 esac
 
 PDF_VIEWER="$ISABELLE_OPEN"
 
 
 ###
 ### Symbol rendering
 ###
 
 ISABELLE_SYMBOLS="$ISABELLE_HOME/etc/symbols:$ISABELLE_HOME_USER/etc/symbols"
 
 
 ###
 ### OCaml
 ###
 
 ISABELLE_OPAM_ROOT="$USER_HOME/.opam"
 
 ISABELLE_OCAML_VERSION="ocaml-base-compiler.4.07.0"
 
 
 ###
 ### Haskell
 ###
 
 ISABELLE_STACK_ROOT="$USER_HOME/.stack"
 
-ISABELLE_STACK_RESOLVER="lts-16.12"
+ISABELLE_STACK_RESOLVER="lts-16.31"
 
 ISABELLE_GHC_VERSION="ghc-8.8.4"
 
 
 ###
 ### Misc settings
 ###
 
 ISABELLE_GNUPLOT="gnuplot"
 ISABELLE_FONTFORGE="fontforge"
 
 #ISABELLE_MLTON="/usr/bin/mlton"
 #ISABELLE_SMLNJ="/usr/bin/sml"
 #ISABELLE_SWIPL="/usr/bin/swipl"