--- a/tests/helpers-testrepo.sh	Sun Apr 08 11:23:55 2018 +0900
+++ b/tests/helpers-testrepo.sh	Sun Apr 08 12:30:59 2018 +0900
@@ -10,7 +10,7 @@
 # system mercurial installation, and may require extensions or settings from
 # the system installation.
 
-if [ -n $HGTESTEXTRAEXTENSIONS ]; then
+if [ -n "$HGTESTEXTRAEXTENSIONS" ]; then
     for extension in $HGTESTEXTRAEXTENSIONS; do
         extraoptions="$extraoptions --config extensions.$extension=!"
     done