diff --git a/VECTO/Input Files/Vehicle.vb b/VECTO/Input Files/Vehicle.vb
index 1c9250971b7fb8b20ba53ac0ee927d20cb67dd20..fab6992313e5068e66aa422c1bcaac5a50538fc1 100644
--- a/VECTO/Input Files/Vehicle.vb	
+++ b/VECTO/Input Files/Vehicle.vb	
@@ -664,7 +664,7 @@ Public Class Vehicle
 	End Get
 	End Property
 
-	Public ReadOnly Property TankSystem As TankSystem Implements IVehicleDeclarationInputData.TankSystem
+	Public ReadOnly Property TankSystem As TankSystem? Implements IVehicleDeclarationInputData.TankSystem
 	get
 			Return DeclarationData.Vehicle.TankSystemDefault
 	End Get
@@ -729,4 +729,6 @@ Public Class Vehicle
 			Return DeclarationData.Vehicle.ADAS.PredictiveCruiseControlDefault
 	End Get
 	End Property
+
+
 End Class
diff --git a/VectoCommon/VectoCommon/InputData/DeclarationInputData.cs b/VectoCommon/VectoCommon/InputData/DeclarationInputData.cs
index 3a77f6525ca9e9835699e2013e56194860c22717..3fa00720bdc440f2275751e801d191be41e0abdf 100644
--- a/VectoCommon/VectoCommon/InputData/DeclarationInputData.cs
+++ b/VectoCommon/VectoCommon/InputData/DeclarationInputData.cs
@@ -142,7 +142,7 @@ namespace TUGraz.VectoCommon.InputData
 
 		bool SleeperCab { get; }
 
-		TankSystem TankSystem { get; }
+		TankSystem? TankSystem { get; }
 
 		IAdvancedDriverAssistantSystemDeclarationInputData ADAS { get; }
 
diff --git a/VectoCore/VectoCore/InputData/FileIO/JSON/JSONComponentInputData.cs b/VectoCore/VectoCore/InputData/FileIO/JSON/JSONComponentInputData.cs
index 7d44789df5e40f3e4f546e6856408d52f345ad11..82d5e86a4f71dfcb7e243a19728ab630abdbcfed 100644
--- a/VectoCore/VectoCore/InputData/FileIO/JSON/JSONComponentInputData.cs
+++ b/VectoCore/VectoCore/InputData/FileIO/JSON/JSONComponentInputData.cs
@@ -304,7 +304,7 @@ namespace TUGraz.VectoCore.InputData.FileIO.JSON
 
 		public bool VocationalVehicle { get { return DeclarationData.Vehicle.VocationalVehicleDefault; } }
 		public bool SleeperCab { get { return DeclarationData.Vehicle.SleeperCabDefault; } }
-		public TankSystem TankSystem { get { return DeclarationData.Vehicle.TankSystemDefault; } }
+		public TankSystem? TankSystem { get { return DeclarationData.Vehicle.TankSystemDefault; } }
 		public IAdvancedDriverAssistantSystemDeclarationInputData ADAS { get { return this; } }
 		public bool ZeroEmissionVehicle { get { return DeclarationData.Vehicle.ZeroEmissionVehicleDefault; } }
 		public bool HybridElectricHDV { get { return DeclarationData.Vehicle.HybridElectricHDVDefault; } }
diff --git a/VectoCore/VectoCore/InputData/FileIO/JSON/JSONVehicleData.cs b/VectoCore/VectoCore/InputData/FileIO/JSON/JSONVehicleData.cs
index 74020e16aad0156f3eea13c49d6b727c5b701bf9..522d802fc27312461cbb39a2b5c5b6b7abb8fff1 100644
--- a/VectoCore/VectoCore/InputData/FileIO/JSON/JSONVehicleData.cs
+++ b/VectoCore/VectoCore/InputData/FileIO/JSON/JSONVehicleData.cs
@@ -260,7 +260,7 @@ namespace TUGraz.VectoCore.InputData.FileIO.JSON
 
 		public bool SleeperCab { get { return DeclarationData.Vehicle.SleeperCabDefault; } }
 
-		public TankSystem TankSystem { get { return DeclarationData.Vehicle.TankSystemDefault; } }
+		public TankSystem? TankSystem { get { return DeclarationData.Vehicle.TankSystemDefault; } }
 		public IAdvancedDriverAssistantSystemDeclarationInputData ADAS { get { return this; } }
 
 		public bool ZeroEmissionVehicle { get { return DeclarationData.Vehicle.ZeroEmissionVehicleDefault; } }
diff --git a/VectoCore/VectoCore/InputData/FileIO/XML/Declaration/XMLDeclarationVehicleDataProvider.cs b/VectoCore/VectoCore/InputData/FileIO/XML/Declaration/XMLDeclarationVehicleDataProvider.cs
index 5ed9d542f59c9614d98c317bcfebf3fb1ec4bc61..35380a991e8d6562e4fe70037770ea064ef5de36 100644
--- a/VectoCore/VectoCore/InputData/FileIO/XML/Declaration/XMLDeclarationVehicleDataProvider.cs
+++ b/VectoCore/VectoCore/InputData/FileIO/XML/Declaration/XMLDeclarationVehicleDataProvider.cs
@@ -269,10 +269,10 @@ namespace TUGraz.VectoCore.InputData.FileIO.XML.Declaration
 				? XmlConvert.ToBoolean(GetElementValue(XMLNames.Vehicle_SleeperCab))
 				: DeclarationData.Vehicle.SleeperCabDefault;
 		} }
-		public TankSystem TankSystem { get {
+		public TankSystem? TankSystem { get {
 			return ElementExists(XMLNames.Vehicle_NgTankSystem)
 				? EnumHelper.ParseEnum<TankSystem>(GetElementValue(XMLNames.Vehicle_NgTankSystem))
-				: DeclarationData.Vehicle.TankSystemDefault;
+				: (TankSystem?)null;
 		} }
 
 		public IAdvancedDriverAssistantSystemDeclarationInputData ADAS { get { return this; } }
diff --git a/VectoCore/VectoCore/InputData/FileIO/XML/Engineering/XMLEngineeringVehicleDataProvider.cs b/VectoCore/VectoCore/InputData/FileIO/XML/Engineering/XMLEngineeringVehicleDataProvider.cs
index 411fd230832c9b9a773ba648231aa29d3b66357f..769b62228da0736052834b937a5e7b9afcae52ec 100644
--- a/VectoCore/VectoCore/InputData/FileIO/XML/Engineering/XMLEngineeringVehicleDataProvider.cs
+++ b/VectoCore/VectoCore/InputData/FileIO/XML/Engineering/XMLEngineeringVehicleDataProvider.cs
@@ -293,7 +293,7 @@ namespace TUGraz.VectoCore.InputData.FileIO.XML.Engineering
 		public IPTOTransmissionInputData PTOTransmissionInputData { get; private set; }
 		public bool VocationalVehicle { get { return false; } }
 		public bool SleeperCab { get { return true; } }
-		public TankSystem TankSystem { get; }
+		public TankSystem? TankSystem { get; }
 		public IAdvancedDriverAssistantSystemDeclarationInputData ADAS { get { return null; } }
 		public bool ZeroEmissionVehicle { get { return false; } }
 		public bool HybridElectricHDV { get { return false; } }