diff --git a/libs/ardour/vst3_plugin.cc b/libs/ardour/vst3_plugin.cc
index 9613d43587..5b4701ded1 100644
--- a/libs/ardour/vst3_plugin.cc
+++ b/libs/ardour/vst3_plugin.cc
@@ -2566,6 +2566,7 @@ VST3PI::automation_state_changed (uint32_t port, AutoState s, boost::weak_ptr<Au
 			break;
 		default:
 			assert (0);
+			return;
 	}
 	extra_ctrl->setParamAutomationMode (id, am);
 }