diff --git a/bin/pt-table-checksum b/bin/pt-table-checksum
index 66b5f7ce..d29f57e1 100755
--- a/bin/pt-table-checksum
+++ b/bin/pt-table-checksum
@@ -3778,7 +3778,7 @@ sub set_nibble_number {
 
 sub nibble_index {
    my ($self) = @_;
-   return lc($self->{index});
+   return $self->{index};
 }
 
 sub statements {
@@ -6400,7 +6400,8 @@ sub main {
             sth  => $sth->{explain_upper_boundary},
             vals => [ @{$boundary->{lower}}, $nibble_iter->chunk_size() ],
          );
-         if ( lc($expl->{key} || '') ne $nibble_iter->nibble_index() ) {
+         if (   lc($expl->{key} || '')
+             ne lc($nibble_iter->nibble_index() || '') ) {
             PTDEBUG && _d('Cannot nibble next chunk, aborting table');
             if ( $o->get('quiet') < 2 ) {
                my $msg
@@ -6468,7 +6469,8 @@ sub main {
                :          0;
 
             # Ensure that MySQL is using the chunk index.
-            if ( lc($expl->{key} || '') ne $nibble_iter->nibble_index() ) {
+            if (   lc($expl->{key} || '')
+                ne lc($nibble_iter->nibble_index() || '') ) {
                PTDEBUG && _d('Chunk', $args{nibbleno}, 'of table',
                   "$tbl->{db}.$tbl->{tbl} not using chunk index, skipping");
                return 0;  # next boundary
@@ -7267,7 +7269,7 @@ sub have_more_chunks {
 
    # The previous chunk index must match the current chunk index,
    # else we don't know what to do.
-   my $chunk_index = $nibble_iter->nibble_index() || '';
+   my $chunk_index = lc($nibble_iter->nibble_index() || '');
    if (lc($last_chunk->{chunk_index}   || '') ne $chunk_index) {
       warn ts("Cannot resume from table $tbl->{db}.$tbl->{tbl} chunk "
          . "$last_chunk->{chunk} because the chunk indexes are different: "
diff --git a/lib/NibbleIterator.pm b/lib/NibbleIterator.pm
index fd8a9ad4..93f9a28c 100644
--- a/lib/NibbleIterator.pm
+++ b/lib/NibbleIterator.pm
@@ -347,7 +347,7 @@ sub set_nibble_number {
 
 sub nibble_index {
    my ($self) = @_;
-   return lc($self->{index});
+   return $self->{index};
 }
 
 sub statements {
diff --git a/t/pt-table-checksum/samples/no-recheck.txt b/t/pt-table-checksum/samples/no-recheck.txt
index bc1eae68..e03c1a8c 100644
--- a/t/pt-table-checksum/samples/no-recheck.txt
+++ b/t/pt-table-checksum/samples/no-recheck.txt
@@ -1,10 +1,10 @@
 Differences on h=127.0.0.1,P=12346
 TABLE CHUNK CNT_DIFF CRC_DIFF CHUNK_INDEX LOWER_BOUNDARY UPPER_BOUNDARY
-sakila.city 1 0 1 primary 1 100
-sakila.city 6 0 1 primary 501 600
+sakila.city 1 0 1 PRIMARY 1 100
+sakila.city 6 0 1 PRIMARY 501 600
 
 Differences on h=127.0.0.1,P=12347
 TABLE CHUNK CNT_DIFF CRC_DIFF CHUNK_INDEX LOWER_BOUNDARY UPPER_BOUNDARY
-sakila.city 1 0 1 primary 1 100
-sakila.city 6 0 1 primary 501 600
+sakila.city 1 0 1 PRIMARY 1 100
+sakila.city 6 0 1 PRIMARY 501 600
 
diff --git a/t/pt-table-sync/basics.t b/t/pt-table-sync/basics.t
index 09020277..e132b02c 100644
--- a/t/pt-table-sync/basics.t
+++ b/t/pt-table-sync/basics.t
@@ -28,7 +28,7 @@ elsif ( !$slave_dbh ) {
    plan skip_all => 'Cannot connect to sandbox slave';
 }
 else {
-   plan tests => 19;
+   plan tests => 21;
 }
 
 $sb->wipe_clean($master_dbh);
@@ -198,6 +198,41 @@ is(
    "Synced diff (bug 911996)"
 );
 
+# Fix bug 927771.
+$sb->load_file('master', 't/pt-table-sync/samples/bug_927771.sql');
+PerconaTest::wait_for_table($slave_dbh, "test.t", "c='j'");
+
+$slave_dbh->do("update test.t set c='z' where id>8");
+
+`$trunk/bin/pt-table-checksum h=127.1,P=12345,u=msandbox,p=msandbox --max-load '' --lock-wait 3 --chunk-size 2 -t test.t --quiet`;
+
+PerconaTest::wait_for_table($slave_dbh, "percona.checksums", "db='test' and tbl='t' and chunk=4");
+
+$output = output(
+   sub {
+      pt_table_sync::main('h=127.1,P=12345,u=msandbox,p=msandbox',
+         qw(--print --execute --replicate percona.checksums),
+         qw(--no-foreign-key-checks))
+   },
+   stderr => 1,
+);
+
+like(
+   $output,
+   qr/REPLACE INTO `test`.`t`\(`id`, `c`\) VALUES \('9', 'i'\)/,
+   "--replicate with uc index (bug 927771)"
+);
+
+my $rows = $slave_dbh->selectall_arrayref("select id, c from test.t where id>8 order by id");
+is_deeply(
+   $rows,
+   [
+      [9,  'i'],
+      [10, 'j'],
+   ],
+   "Synced slaved (bug 927771)"
+);
+
 # #############################################################################
 # Done.
 # #############################################################################
diff --git a/t/pt-table-sync/samples/bug_927771.sql b/t/pt-table-sync/samples/bug_927771.sql
new file mode 100644
index 00000000..928ca429
--- /dev/null
+++ b/t/pt-table-sync/samples/bug_927771.sql
@@ -0,0 +1,18 @@
+drop database if exists test;
+create database test;
+use test;
+create table t (
+  id int auto_increment not null primary key,
+  c  varchar(8) not null
+) engine=innodb;
+insert into test.t values
+  (null, 'a'),
+  (null, 'b'),
+  (null, 'c'),
+  (null, 'd'),
+  (null, 'e'),
+  (null, 'f'),
+  (null, 'g'),
+  (null, 'h'),
+  (null, 'i'),
+  (null, 'j');