Synapse development is promoted by a variety of cell adhesion molecules that connect neurons and organize synaptic proteins. Many of these adhesion molecules are linked to neurodevelopmental disorders; mutations in neuroligin and neurexin proteins, for example, are associated with autism and schizophrenia. A new study reveals that another family of proteins linked to these disorders regulates the function of neuroligins and neurexins in order to suppress the development of inhibitory synapses.