diff --git a/func/main.sh b/func/main.sh
index 5f71bb1f..a92bb59a 100644
--- a/func/main.sh
+++ b/func/main.sh
@@ -551,7 +551,7 @@ is_user_format_valid() {
 is_domain_format_valid() {
     object_name=${2-domain}
     exclude="[!|@|#|$|^|&|*|(|)|+|=|{|}|:|,|<|>|?|_|/|\|\"|'|;|%|\`| ]"
-    if [[ $1 =~ $exclude ]] || [[ $1 =~ ^[0-9]+$ ]] || [[ $1 =~ "\.\." ]] || [[ $1 =~ "$(printf '\t')" ]]; then
+    if [[ $1 =~ $exclude ]] || [[ $1 =~ ^[0-9]+$ ]] || [[ $1 =~ \.\. ]] || [[ $1 =~ $(printf '\t') ]]; then
         check_result $E_INVALID "invalid $object_name format :: $1"
     fi
 }