A Jonny Evans own goal proved enough to give Bulgaria victory over Northern Ireland in Wednesday's friendly.
Northern Ireland's Keith Gillespie is challenged by Mihail Venkon
The only score came in the 38th minute when Martin Petrov fired low across the face of goal and the ball went in off unlucky defender Jonny Evans.
Burnley frontman Kyle Lafferty missed a good chance in the first half when he narrowly failed to get a touch on Chris Brunt's inviting cross from the left.
The result ended Northern Ireland's six-game unbeaten home run.
The match had a low-key opening quarter and NI keeper Maik Taylor was not called into serious action until the 24th minute when he palmed over a header from the unmarked Alexander Tunchev.
Bulgaria should have taken the lead nine minutes before half-time when Tottenham striker Dimitar Berbatov set up Todor Yanchev but his weak shot was blocked.
The visitors deservedly went ahead after Petrov got past Keith Gillespie on the left. Keeper Taylor was exposed and could do little as Petrov fired across goal and the ball went in off Evans.
Northern Ireland manager Nigel Worthington, who had promised to look at as many players as possible, brought on three substitutes at the start of the second half.
Stephen Craigan, Chris Baird and Steve Davis joined the action with Evans, George McCartney and Damien Johnson making way.
Bulgaria continued to make most of the running and Worthington made a further change just before the hour in bringing on Scunthorpe's Martin Paterson for Lafferty.
Petrov shot from a free-kick soon after but Taylor saved an attempt that was probably going wide anyway.
Paterson's first contribution was to win a free-kick on the edge of the area but David Healy's effort was deflected over.
Northern Ireland: Taylor, McAuley, McCartney, Hughes, Evans, Clingan, Gillespie, Johnson, Healy, Lafferty, Brunt.
Subs:Mannus, Baird, Sproule, Webb, Paterson, Davis, Thompson, Robinson, Craigan.
Bulgaria: Petkov, Angelov, Venkov, Tunchev, Tomasic, Milanov, Martin Petrov, Yanchev, Georgiev, Berbatov, Lazarov.
Subs:Ivankov, Karaslavov, Dimitrov, Popov, Domovchiyski.
Referee: Douglas McDonald (Scotland)