diff --git a/scripts/lib/color.sh b/scripts/lib/color.sh
index ee6792290..2e53ae5ae 100755
--- a/scripts/lib/color.sh
+++ b/scripts/lib/color.sh
@@ -20,7 +20,7 @@
 ################################################################################
 
 # shellcheck disable=SC2034
-if [[ ! -v COLOR_OPEN ]]; then
+if [ -z "${COLOR_OPEN+x}" ]; then
     COLOR_OPEN=1
 fi