diff --git a/4dev/tests/CoreLibsConvertByteTest.php b/4dev/tests/CoreLibsConvertByteTest.php
index 0a226f73..bf49af3b 100644
--- a/4dev/tests/CoreLibsConvertByteTest.php
+++ b/4dev/tests/CoreLibsConvertByteTest.php
@@ -240,6 +240,41 @@ final class CoreLibsConvertByteTest extends TestCase
 			\CoreLibs\Convert\Byte::stringByteFormat($input, \CoreLibs\Convert\Byte::BYTE_FORMAT_SI)
 		);
 	}
+
+	/**
+	 * Exceptions tests
+	 *
+	 * @covers ::humanReadableByteFormat
+	 * @testWith [99]
+	 * @testdox Test exception for humanReadableByteFormat with flag $flag
+	 *
+	 * @param  int  $flag
+	 * @return void
+	 */
+	public function testHumanReadableByteFormatException(int $flag): void
+	{
+		$this->expectException(\Exception::class);
+		\CoreLibs\Convert\Byte::humanReadableByteFormat(12, $flag);
+	}
+
+	/**
+	 * Exceptions tests
+	 * can only be 4, try 1,2 and over
+	 *
+	 * @covers ::stringByteFormat
+	 * @testWith [1]
+	 *           [2]
+	 *           [99]
+	 * @testdox Test exception for stringByteFormat with flag $flag
+	 *
+	 * @param  int  $flag
+	 * @return void
+	 */
+	public function testStringByteFormatException(int $flag): void
+	{
+		$this->expectException(\Exception::class);
+		\CoreLibs\Convert\Byte::stringByteFormat(12, $flag);
+	}
 }
 
 // __END__
diff --git a/www/lib/CoreLibs/Convert/Byte.php b/www/lib/CoreLibs/Convert/Byte.php
index 018c93f9..1708f39e 100644
--- a/www/lib/CoreLibs/Convert/Byte.php
+++ b/www/lib/CoreLibs/Convert/Byte.php
@@ -28,7 +28,7 @@ class Byte
 	 * The class itself hast the following defined
 	 * BYTE_FORMAT_NOSPACE [1] turn off spaces between number and suffix
 	 * BYTE_FORMAT_ADJUST  [2] use sprintf to always print two decimals
-	 * BYTE_FORMAT_SI      [3] use si standard 1000 instead of bytes 1024
+	 * BYTE_FORMAT_SI      [4] use si standard 1000 instead of bytes 1024
 	 * To use the constant from outside use class::CONSTANT
 	 *
 	 * @param  string|int|float $bytes bytes as string int or pure int
@@ -37,6 +37,7 @@ class Byte
 	 *                                 BYTE_FORMAT_ADJUST: sprintf adjusted two 2 decimals
 	 *                                 BYTE_FORMAT_SI: use 1000 instead of 1024
 	 * @return string                  converted byte number (float) with suffix
+	 * @throws Exception               1: no valid flag set
 	 */
 	public static function humanReadableByteFormat($bytes, int $flags = 0): string
 	{
@@ -61,6 +62,9 @@ class Byte
 			} else {
 				$si = false;
 			}
+			if ($flags > 7) {
+				throw new \Exception("Invalid flags parameter: $flags", 1);
+			}
 
 			// si or normal
 			$unit = $si ? 1000 : 1024;
@@ -109,12 +113,13 @@ class Byte
 	 * calculates the bytes based on a string with nnG, nnGB, nnM, etc
 	 * NOTE: large exabyte numbers will overflow
 	 * flag allowed:
-	 * BYTE_FORMAT_SI      [3] use si standard 1000 instead of bytes 1024
+	 * BYTE_FORMAT_SI      [4] use si standard 1000 instead of bytes 1024
 	 *
 	 * @param  string|int|float $number any string or number to convert
 	 * @param  int              $flags  bitwise flag with use space turned on
 	 *                                  BYTE_FORMAT_SI: use 1000 instead of 1024
 	 * @return string|int|float         converted value or original value
+	 * @throws Exception                1: no valid flag set
 	 */
 	public static function stringByteFormat($number, int $flags = 0)
 	{
@@ -124,6 +129,9 @@ class Byte
 		} else {
 			$si = false;
 		}
+		if ($flags != 0 && $flags != 4) {
+			throw new \Exception("Invalid flags parameter: $flags", 1);
+		}
 		// matches in regex
 		$matches = [];
 		// all valid units