--- a/src/Tools/Metis/make_metis	Sun May 16 19:37:15 2021 +0200
+++ b/src/Tools/Metis/make_metis	Mon May 17 13:57:19 2021 +1000
@@ -6,6 +6,7 @@
 # A few other ad hoc transformations are performed to ensure that the sources
 # compile within Isabelle on Poly/ML and SML/NJ.
 
+unset CDPATH
 THIS=$(cd "$(dirname "$0")"; echo $PWD)
 make -f Makefile.FILES refresh_FILES
 FILES=$(cat "$THIS/FILES")