The lack of Ca²⁺-dependent inactivation is the hallmark of Cav1.4 the isoform of L-type Ca²⁺-channels. By contrast, the cardiac and smooth muscle isoforms are well known for their pronounced Ca²⁺-dependent inactivation. To investigate the molecular basis of this difference, we constructed (1) a set of chimeric channels of Cav1.2 and Cav1.4 and (2) a series C-terminal deletion mutants of Cav1.2 and Cav1.4. Using a combination of patch clamp experiments, GST pulldowns and coimmunoprecipitation experiments we found that the C-terminal components that form the Ca²⁺ sensor in Cav1.2 are also present and functional in Cav1.4. Ca²⁺-dependent inactivation of this isoform is prohibited by a specific interaction of a distal C-terminal peptide with a region in the proximal C-terminus. Ca²⁺-dependent inactivation of Cav1.4 can be restored by deletion of the distal domain. Furthermore we converted Cav1.2 into a channel lacking Ca²⁺-dependent inactivation. Our results reveal a novel mechanism by which an inhibitory channel domain within the Cav1.4 C-terminus supresses Ca²⁺-dependent inactivation in the presence of the Ca²⁺-sensing apparatus and the machinery for Ca²⁺-dependent inactivation.