diff --git a/bin/pt-table-checksum b/bin/pt-table-checksum
index 15fe63b9..737b21f9 100755
--- a/bin/pt-table-checksum
+++ b/bin/pt-table-checksum
@@ -6096,9 +6096,6 @@ sub main {
    if ( defined $chunk_index && !$chunk_index ) {
       $o->save_error('--chunk-index cannot be an empty string');
    }
-   else {
-      $chunk_index = lc $chunk_index;
-   }
    if ( defined $n_chunk_index_cols
         && (!$n_chunk_index_cols
             || $n_chunk_index_cols =~ m/[^\d]/
@@ -6684,7 +6681,7 @@ sub main {
                      die "Cannot determine the key_len of the chunk index "
                         . "because MySQL chose "
                         . ($expl->{key} ? "the $expl->{key}" : "no") . " index "
-                        . "rather than the " . $nibble_iter->nibble_index()
+                        . "instead of the " . $nibble_iter->nibble_index()
                         . " index for the first lower boundary statement.  "
                         . "See --[no]check-plan in the documentation for more "
                         . "information.";
@@ -7142,10 +7139,9 @@ sub nibble_is_safe {
       if ( !$tbl->{warned}->{not_using_chunk_index}++
            && $o->get('quiet') < 2 ) {
          warn ts("Skipping chunk " . $nibble_iter->nibble_number()
-            . " of table $tbl->{db}.$tbl->{tbl} because MySQL chose "
+            . " of $tbl->{db}.$tbl->{tbl} because MySQL chose "
             . ($expl->{key} ? "the $expl->{key}" : "no") . " index "
-            . " instead of the " . $nibble_iter->nibble_index() . "index.  "
-            . "This warning will not be printed again for this table.\n");
+            . " instead of the " . $nibble_iter->nibble_index() . "index.\n");
       }
       return 0; # not safe
    }
@@ -7164,14 +7160,13 @@ sub nibble_is_safe {
          if ( !$tbl->{warned}->{oversize_chunk}++
               && $o->get('quiet') < 2 ) {
             warn ts("Skipping chunk " . $nibble_iter->nibble_number()
-               . " of table $tbl->{db}.$tbl->{tbl} because it is oversized.  "
+               . " of $tbl->{db}.$tbl->{tbl} because it is oversized.  "
                . "The current chunk size limit is "
                . ($tbl->{chunk_size} * $limit)
                . " rows (chunk size=$tbl->{chunk_size}"
                . " * chunk size limit=$limit), but MySQL estimates "
                . "that there are " . ($expl->{rows} || 0)
-               . " rows in the chunk."
-               . "  This warning will not be printed again for this table.\n");
+               . " rows in the chunk.\n");
          }
          return 0; # not safe
       }
@@ -7185,12 +7180,11 @@ sub nibble_is_safe {
       if ( !$tbl->{warned}->{key_len}++
            && $o->get('quiet') < 2 ) {
          warn ts("Skipping chunk " . $nibble_iter->nibble_number()
-            . " of table $tbl->{db}.$tbl->{tbl} because MySQL chose "
-            . "to use only " . ($expl->{key_len} || 0) . " bytes "
-            . "of the " . ($expl->{key} || '?') . " index.  "
-            . "See --[no]check-plan in the documentation for "
-            . "more information.  This warning will not be printed "
-            . "again for this table.\n");
+            . " of $tbl->{db}.$tbl->{tbl} because MySQL used "
+            . "only " . ($expl->{key_len} || 0) . " bytes "
+            . "of the " . ($expl->{key} || '?') . " index instead of "
+            . $tbl->{key_len} . ".  See the --[no]check-plan documentation "
+            . "for more information.\n");
       }
       return 0; # not safe
    }
diff --git a/t/pt-table-checksum/chunk_index.t b/t/pt-table-checksum/chunk_index.t
index be68f8d8..ab73d711 100644
--- a/t/pt-table-checksum/chunk_index.t
+++ b/t/pt-table-checksum/chunk_index.t
@@ -25,7 +25,7 @@ if ( !$dbh ) {
    plan skip_all => 'Cannot connect to sandbox master';
 }
 else {
-   plan tests => 13;
+   plan tests => 14;
 }
 
 # The sandbox servers run with lock_wait_timeout=3 and it's not dynamic
@@ -185,6 +185,22 @@ cmp_ok(
    "Skipped bad key_len chunks"
 );
 
+# Use --chunk-index:3 to use only the first 3 left-most columns of the index.
+# Can't use bad_plan.t, however, because its row are almost all identical,
+# so using 3 of 4 pk cols creates an infinite loop.
+ok(
+   no_diff(
+      sub {
+         pt_table_checksum::main(
+            $master_dsn, '--max-load', '',
+            qw(--lock-wait-timeout 3 --chunk-size 5000  -t sakila.rental),
+            qw(--chunk-index rental_date:2 --explain --explain));
+      },
+      "t/pt-table-checksum/samples/n-chunk-index-cols.txt",
+   ),
+   "--chunk-index index:n"
+);
+
 # #############################################################################
 # Done.
 # #############################################################################
diff --git a/t/pt-table-checksum/samples/bad-plan-bug-1010232.sql b/t/pt-table-checksum/samples/bad-plan-bug-1010232.sql
new file mode 100644
index 00000000..981eb08e
--- /dev/null
+++ b/t/pt-table-checksum/samples/bad-plan-bug-1010232.sql
@@ -0,0 +1,17 @@
+DROP DATABASE IF EXISTS bad_plan;
+CREATE DATABASE bad_plan;
+USE bad_plan;
+
+CREATE TABLE t (
+  `c1` smallint(5) unsigned NOT NULL,
+  `c2` mediumint(8) unsigned NOT NULL DEFAULT '0',
+  `c3` smallint(5) unsigned NOT NULL DEFAULT '0',
+  `c4` smallint(5) unsigned NOT NULL DEFAULT '0',
+  PRIMARY KEY (`c1`,`c2`,`c3`,`c4`)
+) ENGINE=InnoDB;
+
+INSERT INTO t VALUES
+(1,1,1,1),(1,1,1,2),(1,1,1,3),(1,1,1,4),(1,1,1,5),(1,1,1,6),(1,1,1,7),(1,1,1,8),(1,1,1,9),(1,1,1,10),(1,1,1,11),(1,1,1,12),(1,1,1,13),(1,1,1,14),(1,1,1,15),(1,1,1,16),(1,1,1,17),(1,1,1,18),(1,1,1,19),(1,1,1,20),(1,1,1,21),(1,1,1,22),(1,1,1,23),(1,1,1,24),(1,1,1,25),(1,1,1,26),(1,1,1,27),(1,1,1,28),(1,1,1,29),(1,1,1,30),(1,1,1,31),(1,1,1,32),(1,1,1,33),(1,1,1,34),(1,1,1,35),(1,1,1,36),(1,1,1,37),(1,1,1,38),(1,1,1,39),(1,1,1,40),(1,1,1,41),(1,1,1,42),(1,1,1,43),(1,1,1,44),(1,1,1,45),(1,1,1,46),(1,1,1,47),(1,1,1,48),(1,1,1,49),(1,1,1,50),(1,1,1,51),(1,1,1,52),(1,1,1,53),(1,1,1,54),(1,1,1,55),(1,1,1,56),(1,1,1,57),(1,1,1,58),(1,1,1,59),(1,1,1,60),(1,1,1,61),(1,1,1,62),(1,1,1,63),(1,1,1,64),(1,1,1,65),(1,1,1,66),(1,1,1,67),(1,1,1,68),(1,1,1,69),(1,1,1,70),(1,1,1,71),(1,1,1,72),(1,1,1,73),(1,1,1,74),(1,1,1,75),(1,1,1,76),(1,1,1,77),(1,1,1,78),(1,1,1,79),(1,1,1,80),(1,1,1,81),(1,1,1,82),(1,1,1,83),(1,1,1,84),(1,1,1,85),(1,1,1,86),(1,1,1,87),(1,1,1,88),(1,1,1,89),(1,1,1,90),(1,1,1,91),(1,1,1,92),(1,1,1,93),(1,1,1,94),(1,1,1,95),(1,1,1,96),(1,1,1,97),(1,1,1,98),(1,1,1,99),(1,1,1,100),
+(1,1,2,1),(1,1,2,2),(1,1,2,3),(1,1,2,4),(1,1,2,5),(1,1,2,6),(1,1,2,7),(1,1,2,8),(1,1,2,9),(1,1,2,10),(1,1,2,11),(1,1,2,12),(1,1,2,13),(1,1,2,14),(1,1,2,15),(1,1,2,16),(1,1,2,17),(1,1,2,18),(1,1,2,19),(1,1,2,20),(1,1,2,21),(1,1,2,22),(1,1,2,23),(1,1,2,24),(1,1,2,25),(1,1,2,26),(1,1,2,27),(1,1,2,28),(1,1,2,29),(1,1,2,30),(1,1,2,31),(1,1,2,32),(1,1,2,33),(1,1,2,34),(1,1,2,35),(1,1,2,36),(1,1,2,37),(1,1,2,38),(1,1,2,39),(1,1,2,40),(1,1,2,41),(1,1,2,42),(1,1,2,43),(1,1,2,44),(1,1,2,45),(1,1,2,46),(1,1,2,47),(1,1,2,48),(1,1,2,49),(1,1,2,50),(1,1,2,51),(1,1,2,52),(1,1,2,53),(1,1,2,54),(1,1,2,55),(1,1,2,56),(1,1,2,57),(1,1,2,58),(1,1,2,59),(1,1,2,60),(1,1,2,61),(1,1,2,62),(1,1,2,63),(1,1,2,64),(1,1,2,65),(1,1,2,66),(1,1,2,67),(1,1,2,68),(1,1,2,69),(1,1,2,70),(1,1,2,71),(1,1,2,72),(1,1,2,73),(1,1,2,74),(1,1,2,75),(1,1,2,76),(1,1,2,77),(1,1,2,78),(1,1,2,79),(1,1,2,80),(1,1,2,81),(1,1,2,82),(1,1,2,83),(1,1,2,84),(1,1,2,85),(1,1,2,86),(1,1,2,87),(1,1,2,88),(1,1,2,89),(1,1,2,90),(1,1,2,91),(1,1,2,92),(1,1,2,93),(1,1,2,94),(1,1,2,95),(1,1,2,96),(1,1,2,97),(1,1,2,98),(1,1,2,99),(1,1,2,100);
+
+ANALYZE TABLE bad_plan.t;
diff --git a/t/pt-table-checksum/samples/n-chunk-index-cols.txt b/t/pt-table-checksum/samples/n-chunk-index-cols.txt
new file mode 100644
index 00000000..f08f80ea
--- /dev/null
+++ b/t/pt-table-checksum/samples/n-chunk-index-cols.txt
@@ -0,0 +1,19 @@
+--
+-- sakila.rental
+--
+
+REPLACE INTO `percona`.`checksums` (db, tbl, chunk, chunk_index, lower_boundary, upper_boundary, this_cnt, this_crc) SELECT ?, ?, ?, ?, ?, ?, COUNT(*) AS cnt, COALESCE(LOWER(CONV(BIT_XOR(CAST(CRC32(CONCAT_WS('#', `rental_id`, `rental_date`, `inventory_id`, `customer_id`, `return_date`, `staff_id`, `last_update` + 0, CONCAT(ISNULL(`return_date`)))) AS UNSIGNED)), 10, 16)), 0) AS crc FROM `sakila`.`rental` FORCE INDEX(`rental_date`) WHERE ((`rental_date` > ?) OR (`rental_date` = ? AND `inventory_id` >= ?)) AND ((`rental_date` < ?) OR (`rental_date` = ? AND `inventory_id` <= ?)) /*checksum chunk*/
+
+REPLACE INTO `percona`.`checksums` (db, tbl, chunk, chunk_index, lower_boundary, upper_boundary, this_cnt, this_crc) SELECT ?, ?, ?, ?, ?, ?, COUNT(*), '0' FROM `sakila`.`rental` FORCE INDEX(`rental_date`) WHERE ((`rental_date` < ?) OR (`rental_date` = ? AND `inventory_id` < ?)) ORDER BY `rental_date`, `inventory_id`, `customer_id` /*past lower chunk*/
+
+REPLACE INTO `percona`.`checksums` (db, tbl, chunk, chunk_index, lower_boundary, upper_boundary, this_cnt, this_crc) SELECT ?, ?, ?, ?, ?, ?, COUNT(*), '0' FROM `sakila`.`rental` FORCE INDEX(`rental_date`) WHERE ((`rental_date` > ?) OR (`rental_date` = ? AND `inventory_id` > ?)) ORDER BY `rental_date`, `inventory_id`, `customer_id` /*past upper chunk*/
+
+SELECT /*!40001 SQL_NO_CACHE */ `rental_date`, `rental_date`, `inventory_id` FROM `sakila`.`rental` FORCE INDEX(`rental_date`) WHERE ((`rental_date` > ?) OR (`rental_date` = ? AND `inventory_id` >= ?)) ORDER BY `rental_date`, `inventory_id`, `customer_id` LIMIT ?, 2 /*next chunk boundary*/
+
+1 2005-05-24 22:53:30,2005-05-24 22:53:30,367 2005-07-09 01:17:08,2005-07-09 01:17:08,2388
+2 2005-07-09 01:19:03,2005-07-09 01:19:03,3438 2005-07-31 17:51:23,2005-07-31 17:51:23,2396
+3 2005-07-31 17:53:51,2005-07-31 17:53:51,928 2005-08-22 13:58:23,2005-08-22 13:58:23,2553
+4 2005-08-22 13:59:19,2005-08-22 13:59:19,3704 2006-02-14 15:16:03,2006-02-14 15:16:03,4568
+5  2005-05-24 22:53:30,2005-05-24 22:53:30,367
+6 2006-02-14 15:16:03,2006-02-14 15:16:03,4568 
+