Lincoln defender Tayo Edun was dismissed late on as the Imps and Gillingham drew 0-0 at a windswept LNER Stadium.
The home side were fortunate not to be reduced to 10 men after 13 minutes when Jake Hesketh felled Connor Ogilvie with a high and dangerous challenge, but referee Tom Nield showed lenience by brandishing a yellow card.
The decision enraged Gills manager Steve Evans, who was booked himself a few minutes later as he continued to remonstrate with the officials.
The best chance of the first half fell to City forward Anthony Scully, who volleyed wide from a good position.
At the other end, Max Ehmer was denied by the legs of Lincoln keeper Josh Vickers.
In the second half, Imps substitute Harry Anderson went close twice, heading over from close range and then being denied by goalkeeper Jack Bonham.
A drab affair came to life in the closing stages as the home side were reduced to 10 men when Edun was sent off in the final minute of normal time.
Following an off-the-ball altercation with Brandon Hanlan, the left-back was booked for the second time.