diff --git a/fhem/fhem.pl b/fhem/fhem.pl
index 9ef33eb17..af97d5348 100755
--- a/fhem/fhem.pl
+++ b/fhem/fhem.pl
@@ -3348,9 +3348,11 @@ ReadingsVal($$$)
 
 sub
 ReadingsNum($$$)
-{ 
+{
   my ($d,$n,$default) = @_;
-  return ReadingsVal($d,$n,$default)+0;
+  my $val = ReadingsVal($d,$n,$default);
+  $val =~ s/[^-\.\d]//g;
+  return $val;
 }
 
 sub