Bug in Ods, merged cells broken

[alpha-and-omega]

This is:

• a bug report

What is the expected behavior?

Merged cells should work in Ods format

What is the current behavior?

Merged cells do not work in Ods format

What are the steps to reproduce?

Test code provided, creates and tests files in all merge-supported formats, only Ods fails.
This can be added to tests.

<?php

require __DIR__ . '/vendor/autoload.php';
//////////////////////////////////////////////////////////
// example with merged cells:
$spreadsheet = new \PhpOffice\PhpSpreadsheet\Spreadsheet();
$spreadsheet->setActiveSheetIndex(0);
$spreadsheet->getActiveSheet()->setCellValue('A1', '1');
$spreadsheet->getActiveSheet()->setCellValue('B1', '2');
$spreadsheet->getActiveSheet()->setCellValue('A2', '33');
$spreadsheet->getActiveSheet()->mergeCells('A2:B2');
//////////////////////////////////////////////////////////
// Write in all merge-supported formats:
$Formats = array('Html','Xls','Xlsx','Ods');
foreach( $Formats as $Format)
{
	// create test file:
	$writer = \PhpOffice\PhpSpreadsheet\IOFactory::createWriter($spreadsheet, $Format);
	$file = "merge.".strtolower($Format);
	$writer->save($file);

	// now test:
	if( 1 != calculate_merged_cells($file,$Format) ) die("Format $Format failed, no merged cells found!\n");
}

function calculate_merged_cells($file,$Format)
{
	$reader = \PhpOffice\PhpSpreadsheet\IOFactory::createReader($Format);
	$spreadsheet = $reader->load($file);
	$n = 0;
	foreach ($spreadsheet->getWorksheetIterator() as $worksheet) {
		foreach ($worksheet->getMergeCells() as $cells) {
			var_dump($cells);
			$n++;
		}
	}
	return $n;
}

Which versions of PhpSpreadsheet and PHP are affected?

all including latest development version