In a substantial body of work on a particular group of multilingual speakers, namely heritage speakers, these are often described as deviating from native-like mastery in a variety of ways. In comparison with monolingual controls, heritage speakers are viewed as lagging behind. This paper addresses this issue and argues that monolingual controls should not be dispensed with, but rather they can be used to gain insights into language variation and the processes that shape monolingual and heritage grammars alike.