--- a/lib/scripts/ocamlfind	Thu Mar 21 19:46:26 2019 +0100
+++ b/lib/scripts/ocamlfind	Fri Mar 22 10:36:50 2019 +0100
@@ -4,7 +4,7 @@
 #
 # Invoke ocamlfind via "opam".
 
-if [ -e "$ISABELLE_OPAM_ROOT/config" ]
+if [ -d "$ISABELLE_OPAM_ROOT/$ISABELLE_OCAML_VERSION/bin" ]
 then
   isabelle_opam config exec --switch "$ISABELLE_OCAML_VERSION" -- ocamlfind "$@"
 else