diff --git a/FHEM/98_SVG.pm b/FHEM/98_SVG.pm
index c222b7c53..204e73d52 100755
--- a/FHEM/98_SVG.pm
+++ b/FHEM/98_SVG.pm
@@ -764,7 +764,7 @@ SVG_readgplotfile($$$)
   prSubst($)
   {
     my $v = $pr->{$_[0]};
-    return $_[0] if(!$v);
+    return "%$_[0]%" if(!$v);
     if($v =~ m/^{.*}$/) {
       $cmdFromAnalyze = $v;
       return eval $v;
@@ -878,7 +878,6 @@ SVG_substcfg($$$$$$)
     }
   }
 
-
   $plot =~ s/\r//g;             # For our windows friends...
   $gplot_script =~ s/\r//g;