diff --git a/lib/Froxlor/Idna/IdnaWrapper.php b/lib/Froxlor/Idna/IdnaWrapper.php
index 2665341f..56a64008 100644
--- a/lib/Froxlor/Idna/IdnaWrapper.php
+++ b/lib/Froxlor/Idna/IdnaWrapper.php
@@ -56,7 +56,16 @@ class IdnaWrapper
 	public function encode($to_encode)
 	{
 		$to_encode = $this->isUtf8($to_encode) ? $to_encode : utf8_encode($to_encode);
-		return $this->idna_converter->encode($to_encode);
+		try {
+			return $this->idna_converter->encode($to_encode);
+		} catch (\InvalidArgumentException $iae) {
+			// dirty hack because Mso\IdnaConvert does not specify error-numbers
+			// see https://github.com/phlylabs/idna-convert/issues/11
+			if (strtolower($iae->getMessage()) == 'this is already a punycode string') {
+				return $to_encode;
+			}
+			throw $iae;
+		}
 	}
 
 	/**
diff --git a/lib/Froxlor/Settings/Store.php b/lib/Froxlor/Settings/Store.php
index 476a4024..86fba687 100644
--- a/lib/Froxlor/Settings/Store.php
+++ b/lib/Froxlor/Settings/Store.php
@@ -225,22 +225,22 @@ class Store
 			$idna_convert = new \Froxlor\Idna\IdnaWrapper();
 			$newfieldvalue = $idna_convert->encode($newfieldvalue);
 
-			if (($fielddata['varname'] == 'hostname' && Settings::Get('system.stdsubdomain') == '') || $fielddata['varname'] == 'stdsubdomain')
-			{
+			if (($fielddata['varname'] == 'hostname' && Settings::Get('system.stdsubdomain') == '') || $fielddata['varname'] == 'stdsubdomain') {
 				if ($fielddata['varname'] == 'stdsubdomain' && $newfieldvalue == '') {
 					// clear field, reset stdsubdomain to system-hostname
-					$oldhost = Settings::Get('system.stdsubdomain');
-					$newhost = Settings::Get('system.hostname');
+					$oldhost = $idna_convert->encode(Settings::Get('system.stdsubdomain'));
+					$newhost = $idna_convert->encode(Settings::Get('system.hostname'));
 				} elseif ($fielddata['varname'] == 'stdsubdomain' && Settings::Get('system.stdsubdomain') == '') {
 					// former std-subdomain was system-hostname
-					$oldhost = Settings::Get('system.hostname');
-					$newhost = Settings::Get('system.stdsubdomain');
+					$oldhost = $idna_convert->encode(Settings::Get('system.hostname'));
+					$newhost = $newfieldvalue;
 				} elseif ($fielddata['varname'] == 'stdsubdomain') {
 					// std-subdomain just changed
-					$oldhost = Settings::Get('system.stdsubdomain');
+					$oldhost = $idna_convert->encode(Settings::Get('system.stdsubdomain'));
 					$newhost = $newfieldvalue;
 				} elseif ($fielddata['varname'] == 'hostname' && Settings::Get('system.stdsubdomain') == '') {
-					$oldhost = Settings::Get('system.hostname');
+					// system-hostname has changed and no system-stdsubdomain is not set
+					$oldhost = $idna_convert->encode(Settings::Get('system.hostname'));
 					$newhost = $newfieldvalue;
 				}