diff --git a/tests/test-highlighting.zsh b/tests/test-highlighting.zsh
index a2f1520..3286b6f 100755
--- a/tests/test-highlighting.zsh
+++ b/tests/test-highlighting.zsh
@@ -107,16 +107,18 @@ run_test_internal() {
   for ((i=1; i<=${#expected_region_highlight}; i++)); do
     local -a highlight_zone; highlight_zone=( ${(z)expected_region_highlight[$i]} )
     local todo=
+    integer start=$highlight_zone[1] end=$highlight_zone[2]
     [[ $highlight_zone[3] == NONE ]] && highlight_zone[3]=
     [[ -n "$highlight_zone[4]" ]] && todo=" # TODO $highlight_zone[4]"
-    for j in {$highlight_zone[1]..$highlight_zone[2]}; do
+    for j in {$start..$end}; do
       if [[ "$observed_result[$j]" != "$highlight_zone[3]" ]]; then
         # Escape # as ♯ since the former is illegal in the 'description' part of TAP output
-        echo "not ok $i ${(qqq)BUFFER[$highlight_zone[1],$highlight_zone[2]]//'#'/♯} [$highlight_zone[1],$highlight_zone[2]]: expected ${(qqq)highlight_zone[3]}, observed ${(qqq)observed_result[$j]}.$todo"
+        echo "not ok $i ${(qqq)BUFFER[$start,$end]//'#'/♯} [$start,$end]: expected ${(qqq)highlight_zone[3]}, observed ${(qqq)observed_result[$j]}.$todo"
         continue 2
       fi
     done
     echo "ok $i$todo"
+    unset start end
     unset todo
     unset highlight_zone
   done