diff --git a/src/Data/AlphaNum.php b/src/Data/AlphaNum.php
index 856858c87..a18324854 100644
--- a/src/Data/AlphaNum.php
+++ b/src/Data/AlphaNum.php
@@ -53,6 +53,10 @@ final class AlphaNum extends QRDataModeAbstract{
 	 */
 	public static function validateString(string $string):bool{
 
+		if($string === ''){
+			return false;
+		}
+
 		foreach(str_split($string) as $chr){
 			if(!isset(self::CHAR_TO_ORD[$chr])){
 				return false;
diff --git a/src/Data/Number.php b/src/Data/Number.php
index 193f3cc75..ff38383ba 100644
--- a/src/Data/Number.php
+++ b/src/Data/Number.php
@@ -46,6 +46,10 @@ final class Number extends QRDataModeAbstract{
 	 */
 	public static function validateString(string $string):bool{
 
+		if($string === ''){
+			return false;
+		}
+
 		foreach(str_split($string) as $chr){
 			if(!isset(self::NUMBER_TO_ORD[$chr])){
 				return false;