diff --git a/scripts/purge_images.sh b/scripts/purge_images.sh
index 1e5f38f..3c74499 100755
--- a/scripts/purge_images.sh
+++ b/scripts/purge_images.sh
@@ -15,7 +15,7 @@ find "${EOLAS_PATH}/img" -type f | while read filename; do
     fi
 done
 
-if !$unused_images; then
+if [[ $unused_images == false]]; then
     echo "Nothing to purge: all images currently in use."
 fi