We report results of an experiment exploring the mass/count distinction in Hebrew-speaking 4;4-17;11 year-olds and adults. Adopting Barner & Snedeker’s (2005) experimental methodology we tested how speakers use singular/plural morphology to distinguish nouns that quantify over individuals from nouns that do not. Adult speakers behaved as predicted, quantifying over individuals when faced with count, flexible-count and object-mass nouns, but not when faced with mass or flexible-mass nouns. Conversely, the acquisition pattern was very surprising, with children showing no mass/count distinction before age 7;9. Convergence was later reached, but only to disappear again for teenagers. We suggest that these data may be the result of the growing unimportance of the mass/count distinction in Hebrew.