Gabriel Martinelli's goal was enough to give the Premier League leaders a hard-fought win at Leicester City.
The Brazilian struck in the first minute of the second half, latching on to a deft pass from Leandro Trossard to roll his shot past Danny Ward.
Trossard had a fine first-half goal disallowed after Arsenal's Ben White held Ward in the build-up.
Arsenal lead Manchester City by two points after Pep Guardiola's side beat Bournemouth 4-1 in their Saturday tea-time fixture.
Leicester, who remain 14th, were lacklustre although Kelechi Iheanacho had a goal flagged for offside shortly after Trossard's disallowed effort and Kiernan Dewsbury-Hall curled a shot just wide in the second half.