diff -r 423c0b571f1e -r 2c48be88f847 lib/Tools/ocaml_setup
--- a/lib/Tools/ocaml_setup	Thu Mar 21 15:51:04 2019 +0100
+++ b/lib/Tools/ocaml_setup	Thu Mar 21 16:16:43 2019 +0100
@@ -8,9 +8,9 @@
 
 if [ -e "$ISABELLE_OPAM_ROOT/config" ]
 then
-  isabelle_opam switch create "$ISABELLE_OCAML_VERSION"
+  isabelle_opam switch reinstall -y "$ISABELLE_OCAML_VERSION"
 else
-  isabelle_opam init --disable-sandboxing --no-setup --compiler="$ISABELLE_OCAML_VERSION"
+  isabelle_opam init -y --disable-sandboxing --no-setup --compiler="$ISABELLE_OCAML_VERSION"
 fi
 
 isabelle_opam install zarith -y