How can I make a ComboBox filling the whole cell in a Windows Forms table layout?

Question

My ComboBoxes do not fill their table layout cells completely, unlike the buttons. You can see it in the screenshot.

Buttons and ComboBoxes are Dock = Fill, margins are the same, anchor = top, left.

How can I make them filling the entire cell?

Note: It is this "white space" below the ComboBox I want to get rid off.