After naming pictures in their second language (L2), bilinguals experience difficulty in naming pictures in their native language (L1). This phenomenon, the "L2 after-effect", is a lingering consequence of language control mechanisms regulating the activation of L1 and L2 to facilitate L2 production. Building on the Inhibitory Control model proposed by Green (1998), we propose that how much language control is applied depends on the relative balance between the current activation of L1 and L2. In two experiments, Polish-English bilinguals immersed in their L1 performed a blocked picture-naming task. This paradigm provided a continuous measure of the relative balance between the two languages and made it possible to index engagement of control by measuring the L2 after-effect. The results indicate that the higher the activation level of L1 and the lower the activation level of L2, the bigger the L2 after-effect. The results also revealed an enduring down-regulation of L1 activation level in more language-balanced speakers.