diff --git a/bin/pt-table-checksum b/bin/pt-table-checksum
index bb75b65a..ac4ee8c5 100755
--- a/bin/pt-table-checksum
+++ b/bin/pt-table-checksum
@@ -7690,6 +7690,7 @@ sub main {
             );
 
             # Check each slave for checksum diffs.
+            my $max_diffs = 0;
             foreach my $slave ( @$slaves ) {
                eval {
                   my $diffs = $rc->find_replication_differences(
@@ -7699,8 +7700,9 @@ sub main {
                   );
                   PTDEBUG && _d(scalar @$diffs, 'checksum diffs on',
                      $slave->name());
-                  if ( @$diffs ) {
-                     $tbl->{checksum_results}->{diffs} = scalar @$diffs;
+                  if ( my $n_diffs = scalar @$diffs ) {
+                     # https://bugs.launchpad.net/percona-toolkit/+bug/1030031
+                     $max_diffs = $n_diffs if $n_diffs > $max_diffs;
                   }
                };
                if ($EVAL_ERROR) {
@@ -7714,6 +7716,7 @@ sub main {
                   $tbl->{checksum_results}->{errors}++;
                }
             }
+            $tbl->{checksum_results}->{diffs} = $max_diffs;
          }
 
          # Print table's checksum results if we're not being quiet,
diff --git a/t/pt-table-checksum/bugs.t b/t/pt-table-checksum/bugs.t
index 431a9e18..e0149c9a 100644
--- a/t/pt-table-checksum/bugs.t
+++ b/t/pt-table-checksum/bugs.t
@@ -29,16 +29,20 @@ require "$trunk/bin/pt-table-checksum";
 my $dp = new DSNParser(opts=>$dsn_opts);
 my $sb = new Sandbox(basedir => '/tmp', DSNParser => $dp);
 my $master_dbh = $sb->get_dbh_for('master');
-my $slave_dbh  = $sb->get_dbh_for('slave1');
+my $slave1_dbh = $sb->get_dbh_for('slave1');
+my $slave2_dbh = $sb->get_dbh_for('slave2');
 
 if ( !$master_dbh ) {
    plan skip_all => 'Cannot connect to sandbox master';
 }
-elsif ( !$slave_dbh ) {
+elsif ( !$slave1_dbh ) {
    plan skip_all => 'Cannot connect to sandbox slave1';
 }
+elsif ( !$slave2_dbh ) {
+   plan skip_all => 'Cannot connect to sandbox slave2';
+}
 else {
-   plan tests => 8;
+   plan tests => 9;
 }
 
 # The sandbox servers run with lock_wait_timeout=3 and it's not dynamic
@@ -134,6 +138,32 @@ is(
    "Bug 987393 (Perl 5.8 scoping): checksummed table"
 );
 
+# #############################################################################
+# https://bugs.launchpad.net/percona-toolkit/+bug/1030031
+# pt-table-checksum reports wrong number of DIFFS
+# #############################################################################
+$sb->load_file('master', "$sample/a-z.sql");
+$sb->wait_for_slaves();
+
+# Create 2 diffs on slave1 and 1 diff on slave2.
+$slave1_dbh->do("UPDATE test.t SET c='' WHERE id=5");  # diff on slave1 & 2
+$slave1_dbh->do("SET SQL_LOG_BIN=0");
+$slave1_dbh->do("UPDATE test.t SET c='' WHERE id=20"); # diff only on slave1
+
+# Restore sql_log_bin on slave1 in case later tests use it.
+$slave1_dbh->do("SET SQL_LOG_BIN=1");
+
+$output = output(
+   sub { pt_table_checksum::main(@args, qw(-t test.t --chunk-size 10)) },
+   stderr => 1,
+);
+
+is(
+   PerconaTest::count_checksum_results($output, 'diffs'),
+   2,
+   "Bug 1030031 (wrong DIFFS): 2 diffs"
+);
+
 # #############################################################################
 # Done.
 # #############################################################################
diff --git a/t/pt-table-checksum/samples/a-z.sql b/t/pt-table-checksum/samples/a-z.sql
new file mode 100644
index 00000000..48045580
--- /dev/null
+++ b/t/pt-table-checksum/samples/a-z.sql
@@ -0,0 +1,10 @@
+drop database if exists test;
+create database test;
+use test;
+
+create table t (
+  id  int auto_increment primary key,
+  c   varchar(16) not null
+) engine=innodb;
+
+insert into t values (null, 'a'),(null, 'b'),(null, 'c'),(null, 'd'),(null, 'e'),(null, 'f'),(null, 'g'),(null, 'h'),(null, 'i'),(null, 'j'),(null, 'k'),(null, 'l'),(null, 'm'),(null, 'n'),(null, 'o'),(null, 'p'),(null, 'q'),(null, 'r'),(null, 's'),(null, 't'),(null, 'u'),(null, 'v'),(null, 'w'),(null, 'x'),(null, 'y'),(null, 'z');