Chicago is in the middle of an affordable housing crisis, but developers have been flooding into City Hall lately hoping to get around a new law which would require them to set aside units for low-income families.

The legislation in question went into effect on Sunday, Oct. 11; according to DNAinfo Chicago, it’s intended to promote more affordable housing options in affluent Chicago neighborhoods. The Chicago Business Journal reported that the law was passed by Chicago’s City Council this past March, and it involves heavy financial penalities for developers that fail to incorporate affordable housing units into new housing developments.

At the time the law was passed, there were around 618,000 new single-family housing units being built across the country, and several cities have struggled to ensure that enough affordable housing options are built for low-income residents.

Chicago, in particular, is now requiring that developers set aside 10% of their units to be rented or sold at below-market rates, and it only applies to developments with 10 or more units. If developers fail to do so, they face a penalty of at least $100,000. In certain downtown areas of the city, the fine could be as high as $200,000.

This new requirement is a big change to Chicago’s affordable housing legislation, but lawmakers did write up a caveat: developers could abide by the 2007 version of the law — which didn’t require a certain percentage of low-income units — if they submitted their projects to the City Council by its Sept. 24 meeting and have their project approved within nine months (i.e., before June 2016).

Unsurprisingly, there was an influx of activity at City Hall at the end of September; the Chicago Business Journal stated that residential development applications increased by 46% between August and September, due to the deadline.

City officials and developers are still pretty divided on the issue. While city officials hope to encourage more diversification in the city, many developers have argued that construction costs are far too high in a city like Chicago to justify building new low-income units.

The Home Builders Association of Chicago, for example, filed a lawsuit against the city this past August for “improper taking of private property for public use without proper compensation.”