George Semwogerere started his tenure at Express FC with a 1-0 loss to BUL on Sunday away at the FUFA Technical Centre in Njeru.
Congolese import Jean Pierre Kambale Muhindo broke the Red Eagles when he pounced on a rebound to give the host a last minute win.
The two had locked each other in a stalemate for the entire 90 minutes until the Muhindo moment arrived in the last minute of added time.
The loss, third in a row for Express, leaves them 10th with 21 games after 18 outings.
The cooking oil manufacturers, BUL, climb a place into the top four with 30 points. Their new signing Jimmy Kulaba was named the Pilsner man of the match.