diff --git a/fhem/CHANGED b/fhem/CHANGED
index 841284f6e..22fde6aba 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:  70_BOTVAC: fix processing of set for preferences 
  - feature: 59_Twilight: remove dependencies to global lon/lat settings;
                       now, also several different Twilight devices are possible
  - feature: 72_XiaomiDevice: New fan types 1C / P9
diff --git a/fhem/FHEM/70_BOTVAC.pm b/fhem/FHEM/70_BOTVAC.pm
index ea8ac490f..9a12ef8eb 100755
--- a/fhem/FHEM/70_BOTVAC.pm
+++ b/fhem/FHEM/70_BOTVAC.pm
@@ -35,7 +35,7 @@ use GPUtils qw(:all);
 
 use Time::HiRes qw(gettimeofday);
 use Time::Local qw(timelocal);
-use JSON qw(decode_json encode_json);
+use JSON qw(decode_json encode_json to_json);
 use Digest::SHA qw(hmac_sha256_hex sha1_hex);
 use Encode qw(encode_utf8);
 use MIME::Base64;
@@ -620,7 +620,7 @@ sub Set {
 
     # preferences
     elsif ( grep { $a[1] =~ /$_/x } @preferences ) {
-        my $item = $1;
+        my $item = $a[1];
         my %params;
 
         Log3( $name, 4, "BOTVAC set $name $arg" );
@@ -783,7 +783,7 @@ sub SendCommand {
     else {
         Log3( $name, 4, "BOTVAC $name: REQ $service/$cmd" );
     }
-    Log3( $name, 4, "BOTVAC $name: REQ option $option" )
+    Log3( $name, 4, "BOTVAC $name: REQ option " . (ref($option) eq 'HASH' ? to_json($option) : $option) )
       if ( defined($option) );
     LogSuccessors( $hash, @successor );
 
@@ -1858,14 +1858,8 @@ sub CheckRegistration {
         my @nextCmd = ( $service, $cmd, $option );
         unshift( @successor, [ $service, $cmd, $option ] );
 
-        my @succ_item;
-        my $msg = " successor:";
-        for ( my $i = 0 ; $i < @successor ; $i++ ) {
-            @succ_item = @{ $successor[$i] };
-            $msg .= " $i: ";
-            $msg .= join( ",", map { defined($_) ? $_ : '' } @succ_item );
-        }
-        Log3( $name, 4, "BOTVAC created" . $msg );
+        Log3( $name, 4, "BOTVAC $name: register account" );
+        LogSuccessors( $hash, @successor );
 
         SendCommand( $hash, "sessions", undef, undef, @successor )
           if ( ReadingsVal( $name, ".accessToken", "" ) eq "" );
@@ -2138,7 +2132,9 @@ sub LogSuccessors {
     for ( my $i = 0 ; $i < @successor ; $i++ ) {
         @succ_item = @{ $successor[$i] };
         $msg .= " $i: ";
-        $msg .= join( ",", map { defined($_) ? $_ : '' } @succ_item );
+        $msg .= join( ",",
+            map { defined($_) ? ( ref($_) eq 'HASH' ? to_json($_) : $_ ) : '' }
+              @succ_item );
     }
     Log3( $name, 4, $msg ) if ( @successor > 0 );
 
diff --git a/fhem/t/FHEM/70_BOTVAC/CommandSet.t b/fhem/t/FHEM/70_BOTVAC/CommandSet.t
new file mode 100644
index 000000000..6bedce201
--- /dev/null
+++ b/fhem/t/FHEM/70_BOTVAC/CommandSet.t
@@ -0,0 +1,42 @@
+################################################
+# test Set
+################################################
+package FHEM::BOTVAC;
+
+use strict;
+use warnings;
+use Test::More;
+
+# used to import of FHEM functions from fhem.pl
+use GPUtils qw(:all);
+BEGIN {
+    GP_Import(
+        qw(
+            fhem
+            FhemTestUtils_gotLog
+        )
+    );
+}
+
+# trigger without argument
+fhem('set botvac');
+is(FhemTestUtils_gotLog('set botvac : No Argument given'), 1, 'Match: No Argument given');
+
+# trigger with unknown argument
+fhem('set botvac missing');
+is( FhemTestUtils_gotLog('set botvac missing : Unknown argument missing, choose one of password statusRequest:noArg schedule:on,off syncRobots:noArg pollingMode:on,off'),
+    1, 'Match: Unknown argument missing' );
+
+# trigger preferences
+fhem('setreading botvac pref_filterChangeReminderInterval 3');
+fhem('setreading botvac .secretKey testing');
+fhem('set botvac filterChangeReminderInterval 1');
+is( FhemTestUtils_gotLog('REQ messages/setPreferences'),
+    1, 'Match: REQ messages/setPreferences' );
+is( FhemTestUtils_gotLog('REQ option {"filterChangeReminderInterval":43200}'),
+    1, 'Match: REQ option {"filterChangeReminderInterval":43200}' );
+
+done_testing;
+exit(0);
+
+1;
\ No newline at end of file