diff --git a/plugins/mission/mission_item.cpp b/plugins/mission/mission_item.cpp
index 9bc5298e04..002c397dd5 100644
--- a/plugins/mission/mission_item.cpp
+++ b/plugins/mission/mission_item.cpp
@@ -183,6 +183,8 @@ std::ostream &operator<<(std::ostream &str, MissionItem::CameraAction const &cam
             return str << "CameraAction::STOP_VIDEO";
         case MissionItem::CameraAction::NONE:
             return str << "CameraAction::NONE";
+        default:
+            return str << "Unknown";
     }
 }