diff --git a/cd.sh b/cd.sh
index 819404e..ec6cf1a 100644
--- a/cd.sh
+++ b/cd.sh
@@ -1,3 +1,5 @@
+#! /usr/bin/env bash
+
 CD_DNS_SERVERS=(
 '9.9.9.9'
 )
@@ -25,7 +27,7 @@ CD_STEP=0
 
 function cd_step {
     if [ "${1}" ] ; then
-        CD_STEP=$((CD_STEP+1))
+        ((CD_STEP++))
         echo "
  ↕ ${CD_STEP} ↔ ${1}
 "