Poland’s home market risks more volatility after a government program to subsidize mortgages triggered an abrupt surge in prices as consumers rushed to take advantage of cheap financing.

Dom Development SA warned that the price increases might not be sustainable as money for the state-backed loans quickly runs out. Poland’s biggest homebuilder was a key beneficiary of the program, with its gross profit margin jumping to 31.4% in the third quarter from 26.6% year earlier.

“We are enjoying fatter margins thanks to high demand triggered by subsidies to mortgages,” Chief Executive Officer Jaroslaw Szanajca said on a conference call with investors on Thursday. “But looking from long-term perspective, the rally is way too fast and doesn’t allow to plan the future investments properly.”

Ahead of the election last month, the ruling Law and Justice party initiated an incentive in July to cut annual interest on loans to about 2% for certain buyers. The state stimulus caused housing prices to jump about 20% in major Polish cities, according to real estate researchers.

Local banks alerted that the funds earmarked for the two-year program were already nearing depletion as more than 67,000 households filed for the cheap loans by mid-November.

The extent of the market disruption will depend on whether Civic Platform, the biggest party among opposition bloc that won Oct. 15 vote, carries out campaign pledges amid concerns the market is overheating. The group had earlier sought to sweeten the mortgage stimulus and offer loans with no interest at all.