diff --git a/source/RobotAPI/interface/units/UnitInterface.ice b/source/RobotAPI/interface/units/UnitInterface.ice
index 853e3c755afcf91344b36ab2969e0ce735559f40..5cc9073ae4ba23476177d5604b08420ebf6862bc 100644
--- a/source/RobotAPI/interface/units/UnitInterface.ice
+++ b/source/RobotAPI/interface/units/UnitInterface.ice
@@ -46,6 +46,7 @@ module armarx
 	**/
     enum UnitExecutionState
     {
+        eUndefinedUnitExecutionState,
         eUnitConstructed,
         eUnitInitialized,
         eUnitStarted,