The invention relates to besylate and tosylate salts of {8-fluoro-2-[4-(3-methoxyphenyl)piperazin-1-yl]-3-[2-methoxy-5-(trifluoromethyl)phenyl]-3,4-dihydroquinazolin-4-yl}acetic acid and solvates thereof, to the use thereof in a method of treating find/or preventing virus infections, find to the use thereof to produce drugs for use in treating and/or preventing diseases, in particular use as antiviral agents, in particular against cytomegaloviruses (FIG. 1).