diff --git a/bin/pt-online-schema-change b/bin/pt-online-schema-change
index fe920652..a3014931 100755
--- a/bin/pt-online-schema-change
+++ b/bin/pt-online-schema-change
@@ -4755,6 +4755,11 @@ sub next {
             return;
          }
       }
+      if ( !$self->{one_nibble} && !$self->{first_lower} ) {
+         PTDEBUG && _d('No first lower boundary, table must be empty');
+         $self->{no_more_boundaries} = 1;
+         return;
+      }
    }
 
    NIBBLE:
@@ -6502,13 +6507,21 @@ sub main {
          my $tbl         = $args{tbl};
          my $nibble_iter = $args{NibbleIterator};
          my $statements  = $nibble_iter->statements();
+         my $boundary    = $nibble_iter->boundaries();
 
          if ( $o->get('dry-run') ) {
             print "Not copying rows because this is a dry run.\n";
          }
          else {
-            print "Copying approximately ", $nibble_iter->row_estimate(),
-               " rows...\n";
+            if ( !$nibble_iter->one_nibble() && !$boundary->{first_lower} ) {
+               # https://bugs.launchpad.net/percona-toolkit/+bug/1020997
+               print "$tbl->{name} is empty, no rows to copy.\n";
+               return;
+            }
+            else {
+               print "Copying approximately ", $nibble_iter->row_estimate(),
+                  " rows...\n";
+            }
          }
 
          if ( $o->get('print') ) {
diff --git a/lib/NibbleIterator.pm b/lib/NibbleIterator.pm
index a43bcf4e..e1a42703 100644
--- a/lib/NibbleIterator.pm
+++ b/lib/NibbleIterator.pm
@@ -286,6 +286,11 @@ sub next {
             return;
          }
       }
+      if ( !$self->{one_nibble} && !$self->{first_lower} ) {
+         PTDEBUG && _d('No first lower boundary, table must be empty');
+         $self->{no_more_boundaries} = 1;
+         return;
+      }
    }
 
    # If there's another nibble, fetch the rows within it.
diff --git a/t/lib/NibbleIterator.t b/t/lib/NibbleIterator.t
index 8b8e8e5b..1fc4cb22 100644
--- a/t/lib/NibbleIterator.t
+++ b/t/lib/NibbleIterator.t
@@ -249,7 +249,7 @@ is_deeply(
    \@rows,
    $all_rows,
    '1 nibble'
-) or print Dumper(\@rows);
+) or diag(Dumper(\@rows));
 
 # ############################################################################
 # single row table
@@ -274,7 +274,7 @@ is_deeply(
    \@rows,
    [['d']],
    'single row table'
-) or print Dumper(\@rows);
+) or diag(Dumper(\@rows));
 
 # ############################################################################
 # empty table
@@ -294,7 +294,7 @@ is_deeply(
    \@rows,
    [],
    'empty table'
-) or print Dumper(\@rows);
+) or diag(Dumper(\@rows));
 
 # ############################################################################
 # Callbacks
@@ -397,35 +397,35 @@ is_deeply(
    $row,
    [25, 'da79784d'],
    "SELECT chunk checksum 1 FROM sakila.country"
-) or print STDERR Dumper($row); 
+) or diag(Dumper($row));
 
 $row = $ni->next();
 is_deeply(
    $row,
    [25, 'e860c4f9'],
    "SELECT chunk checksum 2 FROM sakila.country"
-) or print STDERR Dumper($row); 
+) or diag(Dumper($row));
 
 $row = $ni->next();
 is_deeply(
    $row,
    [25, 'eb651f58'],
    "SELECT chunk checksum 3 FROM sakila.country"
-) or print STDERR Dumper($row); 
+) or diag(Dumper($row));
 
 $row = $ni->next();
 is_deeply(
    $row,
    [25, '2d87d588'],
    "SELECT chunk checksum 4 FROM sakila.country"
-) or print STDERR Dumper($row); 
+) or diag(Dumper($row));
 
 $row = $ni->next();
 is_deeply(
    $row,
    [9, 'beb4a180'],
    "SELECT chunk checksum 5 FROM sakila.country"
-) or print STDERR Dumper($row); 
+) or diag(Dumper($row));
 
 
 # #########################################################################
@@ -552,7 +552,7 @@ is_deeply(
       [ 'z'        ], # last nibble
    ],
    "Change chunk size while nibbling"
-) or print STDERR Dumper(\@rows);
+) or diag(Dumper(\@rows));
 
 # ############################################################################
 # Nibble one row at a time.