diff --git a/fhem/CHANGED b/fhem/CHANGED
index c0eba9ad4..2077c8efd 100644
--- a/fhem/CHANGED
+++ b/fhem/CHANGED
@@ -1,5 +1,6 @@
 # Add changes at the top of the list. Keep it in ASCII, and 80-char wide.
 # Do not insert empty lines here, update check depends on it.
+  - bugfix:  00_MQTT: fix Undef
   - feature: 83_IOhomecontrol: new attribute setCmds
   - bugfix:  00_MQTT: added delete 
   - new:     83_IOhomecontrol: control IOhomecontrol devices via REST API
diff --git a/fhem/FHEM/00_MQTT.pm b/fhem/FHEM/00_MQTT.pm
index 6baefaab9..236806b40 100644
--- a/fhem/FHEM/00_MQTT.pm
+++ b/fhem/FHEM/00_MQTT.pm
@@ -133,9 +133,6 @@ sub Define($$) {
 sub Undef($) {
   my $hash = shift;
   Stop($hash);
-  my $name = $hash->{NAME};
-  setKeyValue($name."_user",undef);
-  setKeyValue($name."_pass",undef);
   return undef;
 }