Celtic have registered a narrow 1-0 half-time lead away to Astra Giurgiu in the Europa League tonight.
Ronny Deila's side fashioned the first clear chance of the game as Johansen forced Silviu Lung Jr into a smart finger-tip save after 16 minutes.
The Bhoys continued to dominate but Craig Gordon had to be alert to palm away Seidu Yahaya's thumping drive on 27 minutes.
The visitors brushed off that scare then moved ahead through Johansen, who struck a fine volley into the top corner to give Lung no chance.
Celtic had further chances to improve on their lead prior to the break, with Lung denying Wakaso Mubarak, before the Romanian then thwarted Charlie Mulgrew on the stroke of half time.
