Command Blocks don't save text when opening them.

When I open a command block and type a command, it's able to run it but when I re-open the command block, it doesn't save what I typed in so I'm unable to edit it.

•Place down command block.

•Write down a command in the command block, for example '/say hello!'

•Click 'Done'

•Open command block

•Command block is blank and text is not saved