diff --git a/fhem/FHEM/11_FHT.pm b/fhem/FHEM/11_FHT.pm
index 03e849447..6c1257d80 100755
--- a/fhem/FHEM/11_FHT.pm
+++ b/fhem/FHEM/11_FHT.pm
@@ -185,6 +185,7 @@ FHT_Initialize($)
   $hash->{DefFn}     = "FHT_Define";
   $hash->{UndefFn}   = "FHT_Undef";
   $hash->{ParseFn}   = "FHT_Parse";
+  $hash->{StateFn}   = "FHT_State";
   $hash->{AttrList}  = "IODev do_not_notify:1,0 model:fht80b dummy:1,0 " .
                        "showtime:1,0 retrycount " .
                        "minfhtbuffer lazy tmpcorr ignore:1,0 ".
@@ -566,7 +567,7 @@ FHT_Parse($$)
     Log3 $name, 4, "FHT $name windowsensor: $valSensor";
   }
 
-  $cmd = "FHZ:$cmd" if(substr($msg,24,1) eq "7");
+  $cmd = "FHZ_$cmd" if(substr($msg,24,1) eq "7");
 
   readingsBulkUpdate($def, $cmd, $val);
   if($cmd eq "measured-temp") {
@@ -704,6 +705,21 @@ getFhtBuffer($)
   }
 }
 
+#####################################
+# Remap the old FHZ: readingnames to FHZ_
+sub
+FHT_State($$$$)
+{
+  my ($hash, $tim, $rname, $rval) = @_;
+
+  return undef if($rname !~ m/^FHZ:/);
+
+  my $newname = $rname;
+  $newname =~ s/:/_/g;
+  setReadingsVal($hash, $newname, $rval, $tim);
+  return "FHT: renamed reading $rname to $newname for $hash->{NAME}";
+}
+
 1;
 
 =pod
diff --git a/fhem/fhem.pl b/fhem/fhem.pl
index 72f222ec7..5dfc5892b 100755
--- a/fhem/fhem.pl
+++ b/fhem/fhem.pl
@@ -2548,6 +2548,10 @@ CommandSetstate($$)
         next;
       }
 
+      Log3 $d, 3, "WARNING: unsupported character in reading $sname ".
+             "(not A-Za-z\\d_\\.-), notify the $d->{TYPE} module maintainer."
+        if($sname !~ m/^[A-Za-z\d_\.-]+$/);
+
       if(!defined($d->{READINGS}{$sname}) ||
          !defined($d->{READINGS}{$sname}{TIME}) ||
          $d->{READINGS}{$sname}{TIME} lt $tim) {
@@ -3796,6 +3800,12 @@ readingsBeginUpdate($)
   my ($hash)= @_;
   my $name = $hash->{NAME};
   
+  if(!$name) {
+    Log 1, "ERROR: empty name in readingsBeginUpdate";
+    stacktrace();
+    return;
+  }
+
   # get timestamp
   my $now = gettimeofday();
   my $fmtDateTime = FmtDateTime($now);