Combobox inside toolbar - trigger does not align properly

I have a combobox inside a toolbar, but the trigger (down arrow) isn't aligned with the box. (I have tested in current Chrome and IE). Here's the relevant portion of my code:

Code:

Ext.define('Maverick.grid.techClockEntries', {        extend: 'Ext.grid.Panel',
        id: 'tech-clock-entries-grid',
        renderTo: Ext.get('tech-clock-entries-grid-container'),
        store: techClockEntriesStore,
        features: [filtersCfg],
        title: 'Tech Clock Entries',
        columns: [{ ... }],
dockedItems: [{
            xtype: 'toolbar',
            id: 'tech-clock-entries-grid-toolbar',
            store: techClockEntriesStore,  
            dock: 'top',
            displayInfo: true,
            items: [
                {
                    xtype: 'combo'
                }
            ]
        }

[

... and here's what it looks like:

Screenshot - 6_16_2014 , 10_29_12 PM.jpg

Can anyone give me any idea what I'm doing wrong?