diff --git a/common/types.hpp b/common/types.hpp
index 318dc7e..865f2c4 100644
--- a/common/types.hpp
+++ b/common/types.hpp
@@ -41,6 +41,7 @@
 using CompositeCount = uint8_t;
 using SensorOffset = uint8_t;
 using EventState = uint8_t;
+using TerminusValidity = uint8_t;
 
 //!< Subset of the State Set that is supported by a effecter/sensor
 using PossibleStates = std::set<uint8_t>;