Critics say the move is designed to prolong President Joseph Kabila's time in office.
Tuesday's protests, in which vehicles were burnt and main streets in the city blocked, came a day after clashes between police and demonstrators left at least four people dead, according to witnesses.
The revision to the electoral law was approved late on Saturday in a vote that many opposition lawmakers boycotted.
Opposition leaders had called for demonstrations against the measure, which is to be considered by the Senate.
Kabila assumed office in 2001.
The constitution prevents him from running again.
His supporters say the census measure has been needlessly politicised, but opposition leaders argue that logistical challenges for the census meant next year's election would need to be delayed.
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- Democratic Republic of Congo