Laser-heated diamond-anvil cell (LHDAC) experiments reveal electronic changes in KBr at pressures between ∼13-81GPa when heated to high temperatures that cause runaway heating to temperatures in excess of ∼5000K. The drastic changes in absorption behavior of KBr are interpreted as rapid formation of high-pressure F-center defects. The defects are localized to the heated region and thus do not change the long-range crystalline order of KBr. The results have significant consequences for temperature measurements in LHDAC experiments and extend the persistence of F centers in alkali halides to at least 81 GPa. © 2018 American Physical Society.