diff --git a/4dev/tests/CoreLibsConvertStringsTest.php b/4dev/tests/CoreLibsConvertStringsTest.php
index 7e71355f..9f054928 100644
--- a/4dev/tests/CoreLibsConvertStringsTest.php
+++ b/4dev/tests/CoreLibsConvertStringsTest.php
@@ -97,7 +97,13 @@ final class CoreLibsConvertStringsTest extends TestCase
 				'2-2',
 				null,
 				'12--3-4'
-			]
+			],
+			'mutltibyte string' => [
+				'あいうえ',
+				'2-2',
+				null,
+				'あいうえ'
+			],
 		];
 	}
 
diff --git a/www/admin/class_test.strings.php b/www/admin/class_test.strings.php
index 7681110d..4e08b2fa 100644
--- a/www/admin/class_test.strings.php
+++ b/www/admin/class_test.strings.php
@@ -64,6 +64,13 @@ $string = '1234';
 print "Convert: $string with $split to: "
 	. \CoreLibs\Convert\Strings::splitFormatString($string, $split)
 	. "<br>";
+$split = '2-2';
+$string = 'あいうえ';
+print "Convert: $string with $split to: "
+	. \CoreLibs\Convert\Strings::splitFormatString($string, $split)
+	. "<br>";
+
+
 
 // error message
 print $log->printErrorMsg();
diff --git a/www/lib/CoreLibs/Convert/Strings.php b/www/lib/CoreLibs/Convert/Strings.php
index 324083af..a820fcdc 100644
--- a/www/lib/CoreLibs/Convert/Strings.php
+++ b/www/lib/CoreLibs/Convert/Strings.php
@@ -35,6 +35,14 @@ class Strings
 		if (empty($split_format)) {
 			return $value;
 		}
+		// if not in the valid ASCII character range
+		// might need some tweaking
+		if (preg_match('/[^\x20-\x7e]/', $value)) {
+			return $value;
+		}
+		// if (!mb_check_encoding($value, 'ASCII')) {
+		// 	return $value;
+		// }
 		$split_list = preg_split(
 			// allowed split characters
 			"/([" . $split_charcters . "]{1})/",