diff --git a/scripts/pi-hole/php/func.php b/scripts/pi-hole/php/func.php
index 4453d99d..22840bdb 100644
--- a/scripts/pi-hole/php/func.php
+++ b/scripts/pi-hole/php/func.php
@@ -8,9 +8,9 @@
 
 function is_valid_domain_name($domain_name)
 {
-    return (preg_match("/^([a-z\d](-*[a-z\d])*)(\.([a-z\d](-*[a-z\d])*))*$/i", $domain_name) &&  //valid chars check
-        preg_match("/^.{1,253}$/", $domain_name) && //overall length check
-        preg_match("/^[^\.]{1,63}(\.[^\.]{1,63})*$/", $domain_name)); //length of each label
+    return (preg_match("/^((-|_)*[a-z\d]((-|_)*[a-z\d])*(-|_)*)(\.(-|_)*([a-z\d]((-|_)*[a-z\d])*))*$/i", $domain_name) // Valid chars check
+        preg_match("/^.{1,253}$/", $domain_name) && // Overall length check
+        preg_match("/^[^\.]{1,63}(\.[^\.]{1,63})*$/", $domain_name)); // Length of each label
 }
 
 function checkfile($filename) {
diff --git a/scripts/pi-hole/php/queryads.php b/scripts/pi-hole/php/queryads.php
index 457e235c..171e5d52 100644
--- a/scripts/pi-hole/php/queryads.php
+++ b/scripts/pi-hole/php/queryads.php
@@ -22,9 +22,9 @@ function echoEvent($datatext) {
 // Credit: http://stackoverflow.com/a/4694816/2087442
 function is_valid_domain_name($domain_name)
 {
-    return (preg_match("/^([a-z\d](-*[a-z\d])*)(\.([a-z\d](-*[a-z\d])*))*$/i", $domain_name) //valid chars check
-            && preg_match("/^.{1,253}$/", $domain_name) //overall length check
-            && preg_match("/^[^\.]{1,63}(\.[^\.]{1,63})*$/", $domain_name)   ); //length of each label
+    return (preg_match("/^((-|_)*[a-z\d]((-|_)*[a-z\d])*(-|_)*)(\.(-|_)*([a-z\d]((-|_)*[a-z\d])*))*$/i", $domain_name) // Valid chars check
+            && preg_match("/^.{1,253}$/", $domain_name) // Overall length check
+            && preg_match("/^[^\.]{1,63}(\.[^\.]{1,63})*$/", $domain_name)   ); // Length of each label
 }
 
 // Test if domain is set