diff --git a/cpu/saml21/periph/pm.c b/cpu/saml21/periph/pm.c
index 9bc2d8a871ea30632127711f50e1496e639e0d8e..7806ab6ef9dec132f85fcf8df96e2862b1743013 100644
--- a/cpu/saml21/periph/pm.c
+++ b/cpu/saml21/periph/pm.c
@@ -38,6 +38,7 @@ void pm_set(unsigned mode)
                 DEBUG("pm_set(): setting STANDBY mode.\n");
                 _mode = PM_SLEEPCFG_SLEEPMODE_STANDBY;
                 break;
+            default: /* Falls through */
             case 2:
                 DEBUG("pm_set(): setting IDLE mode.\n");
                 _mode = PM_SLEEPCFG_SLEEPMODE_IDLE2;