diff --git a/lib/JSONReportFormatter.pm b/lib/JSONReportFormatter.pm
index ab981ade..807334f0 100644
--- a/lib/JSONReportFormatter.pm
+++ b/lib/JSONReportFormatter.pm
@@ -1,3 +1,22 @@
+# This program is copyright 2013 Percona Ireland Ltd.
+# Feedback and improvements are welcome.
+#
+# THIS PROGRAM IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED
+# WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
+# MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
+#
+# This program is free software; you can redistribute it and/or modify it under
+# the terms of the GNU General Public License as published by the Free Software
+# Foundation, version 2; OR the Perl Artistic License.  On UNIX and similar
+# systems, you can issue `man perlgpl' or `man perlartistic' to read these
+# licenses.
+#
+# You should have received a copy of the GNU General Public License along with
+# this program; if not, write to the Free Software Foundation, Inc., 59 Temple
+# Place, Suite 330, Boston, MA  02111-1307  USA.
+# ###########################################################################
+# JSONReportFormatter package
+# ###########################################################################
 {
 package JSONReportFormatter;
 use Lmo;
@@ -57,8 +76,6 @@ override query_report => sub {
 
    my @attribs = @{$ea->get_attributes()};
 
-   my %string_args = map { $_ => 1 } qw( db host arg user bytes pos_in_log );
-   
    my @queries;
    foreach my $worst_info ( @$worst ) {
       my $item   = $worst_info->[0];
@@ -98,7 +115,7 @@ override query_report => sub {
             $class{ts_min} = $ts->{min};
             $class{ts_max} = $ts->{max};
          }
-         elsif ( $string_args{$attrib} ) {
+         elsif ( ($ea->{type_for}->{$attrib} || '') eq 'str' ) {
             $metrics{$attrib} = { value => $metrics{$attrib}{max} }; 
          }
          elsif ( ($ea->{type_for}->{$attrib} || '') eq 'num' ) {
@@ -128,3 +145,6 @@ override query_report => sub {
 no Lmo;
 1;
 }
+# ###########################################################################
+# End JSONReportFormatter package
+# ###########################################################################
diff --git a/t/pt-query-digest/output.t b/t/pt-query-digest/json.t
similarity index 98%
rename from t/pt-query-digest/output.t
rename to t/pt-query-digest/json.t
index f61bb572..21513543 100644
--- a/t/pt-query-digest/output.t
+++ b/t/pt-query-digest/json.t
@@ -28,7 +28,7 @@ ok(
       "$results/empty_report.txt",
    ),
    'json output for empty log'
-);
+) or diag($test_diff);
 
 ok(
    no_diff(
diff --git a/t/pt-query-digest/samples/empty_report.txt b/t/pt-query-digest/samples/empty_report.txt
index a05997d5..e69de29b 100644
--- a/t/pt-query-digest/samples/empty_report.txt
+++ b/t/pt-query-digest/samples/empty_report.txt
@@ -1,2 +0,0 @@
-
-# No events processed.