diff --git a/scripts/pi-hole/php/func.php b/scripts/pi-hole/php/func.php
index 1573e5d6..c2e42b48 100644
--- a/scripts/pi-hole/php/func.php
+++ b/scripts/pi-hole/php/func.php
@@ -8,12 +8,27 @@
 
 // Credit: http://stackoverflow.com/a/4694816/2087442
 // Modified because of https://github.com/pi-hole/AdminLTE/pull/533
-function validDomain($domain_name)
+ini_set("pcre.recursion_limit", 1500);
+function validDomain($domain_name, &$message = NULL)
 {
-	$validChars = preg_match("/^((-|_)*[a-z\d]((-|_)*[a-z\d])*(-|_)*)(\.(-|_)*([a-z\d]((-|_)*[a-z\d])*))*$/i", $domain_name);
-	$lengthCheck = preg_match("/^.{1,253}$/", $domain_name);
-	$labelLengthCheck = preg_match("/^[^\.]{1,63}(\.[^\.]{1,63})*$/", $domain_name);
-	return ( $validChars && $lengthCheck && $labelLengthCheck ); //length of each label
+	if(!preg_match("/^((-|_)*[a-z\d]((-|_)*[a-z\d])*(-|_)*)(\.(-|_)*([a-z\d]((-|_)*[a-z\d])*))*$/i", $domain_name)) {
+		if($message !== NULL)
+			$message = "it contains invalid characters";
+		return false;
+	}
+	if(!preg_match("/^.{1,253}$/", $domain_name)) {
+		if($message !== NULL)
+			$message = "its length is invalid";
+		return false;
+	}
+	if(!preg_match("/^[^\.]{1,63}(\.[^\.]{1,63})*$/", $domain_name)) {
+		if($message !== NULL)
+			$message = "at least one label is of invalid length";
+		return false;
+	}
+
+	// everything is okay
+	return true;
 }
 
 function validDomainWildcard($domain_name)
diff --git a/scripts/pi-hole/php/groups.php b/scripts/pi-hole/php/groups.php
index ec27b6ef..838dbf83 100644
--- a/scripts/pi-hole/php/groups.php
+++ b/scripts/pi-hole/php/groups.php
@@ -646,15 +646,16 @@ if ($_POST['action'] == 'get_groups') {
             {
                 // If adding to the exact lists, we convert the domain lower case and check whether it is valid
                 $domain = strtolower($domain);
-                if(validDomain($domain))
+                $msg = "";
+                if(!validDomain($domain, $msg))
                 {
                     // This is the case when idn_to_ascii() modified the string
                     if($input !== $domain && strlen($domain) > 0)
-                        $errormsg = 'Domain ' . htmlentities($input) . ' (converted to "' . htmlentities(utf8_encode($domain)) . '") is not a valid domain.';
+                        $errormsg = 'Domain ' . htmlentities($input) . ' (converted to "' . htmlentities(utf8_encode($domain)) . '") is not a valid domain because ' . $msg . '.';
                     elseif($input !== $domain)
-                        $errormsg = 'Domain ' . htmlentities($input) . ' is not a valid domain.';
+                        $errormsg = 'Domain ' . htmlentities($input) . ' is not a valid domain because ' . $msg . '.';
                     else
-                        $errormsg = 'Domain ' . htmlentities(utf8_encode($domain)) . ' is not a valid domain.';
+                        $errormsg = 'Domain ' . htmlentities(utf8_encode($domain)) . ' is not a valid domain because ' . $msg . '.';
                     throw new Exception($errormsg . '<br>Added ' . $added . " out of ". $total . " domains");
                 }
             }
diff --git a/scripts/pi-hole/php/queryads.php b/scripts/pi-hole/php/queryads.php
index 4302d561..38d4e8d2 100644
--- a/scripts/pi-hole/php/queryads.php
+++ b/scripts/pi-hole/php/queryads.php
@@ -9,6 +9,7 @@
 while (ob_get_level() > 0) {
     ob_end_flush();
 }
+require_once("func.php");
 ini_set("output_buffering", "0");
 ob_implicit_flush(true);
 header('Content-Type: text/event-stream');
@@ -21,16 +22,6 @@ function echoEvent($datatext) {
       echo $datatext;
 }
 
-// Credit: http://stackoverflow.com/a/4694816/2087442
-ini_set("pcre.recursion_limit", 1500);
-function validDomain($domain_name)
-{
-    return ($domain_name[0] !== '-' // Don't allow domains to appear as command line options
-            && preg_match("/^((-|_)*[a-z\d]((-|_)*[a-z\d])*(-|_)*)(\.(-|_)*([a-z\d]((-|_)*[a-z\d])*))*$/i", $domain_name) // Valid chars check
-            && preg_match("/^.{1,253}$/", $domain_name) // Overall length check
-            && preg_match("/^[^\.]{1,63}(\.[^\.]{1,63})*$/", $domain_name)   ); // Length of each label
-}
-
 // Test if domain is set
 if(isset($_GET["domain"]))
 {