diff --git a/VectoCommon/VectoCommon/Utils/SI.cs b/VectoCommon/VectoCommon/Utils/SI.cs
index 6a66126612d25aeb5c5282ea6d8fd6790c4f888c..4f9ad9d4f424fcb2bc1acf6611d96c939d3a3ec2 100644
--- a/VectoCommon/VectoCommon/Utils/SI.cs
+++ b/VectoCommon/VectoCommon/Utils/SI.cs
@@ -579,6 +579,11 @@ namespace TUGraz.VectoCommon.Utils
 		private KilogramPerWattSecond(double val) : base(val, Units) { }
 
 		public override string UnitString { get { return "kg/Ws"; } }
+
+		public static Kilogram operator *(KilogramPerWattSecond kpws, WattSecond ws)
+		{
+			return SIBase<Kilogram>.Create(kpws.Val * ws.Value());
+		}
 	}
 
 	/// <summary>
@@ -599,6 +604,11 @@ namespace TUGraz.VectoCommon.Utils
 		{
 			return SIBase<Watt>.Create(wattSecond.Val / second.Value());
 		}
+
+		public static Kilogram operator *(WattSecond ws, KilogramPerWattSecond kpws)
+		{
+			return SIBase<Kilogram>.Create(ws.Val * kpws.Value());
+		}
 	}
 
 	public class WattSecondPerCubicMeter : SIBase<WattSecondPerCubicMeter>