diff --git a/z.sh b/z.sh
index 41ea532..da629ae 100644
--- a/z.sh
+++ b/z.sh
@@ -44,7 +44,7 @@ _z() {
         # don't track excluded directory trees
         local exclude
         for exclude in "${_Z_EXCLUDE_DIRS[@]}"; do
-            case "$*" in $exclude*) return;; esac
+            case "$*" in "$exclude*") return;; esac
         done
 
         # maintain the data file