diff --git a/VectoCommon/VectoCommon/Utils/SI.cs b/VectoCommon/VectoCommon/Utils/SI.cs
index 04d232b4fb4c0d95ea95432670fa6a4b5479c810..791cc3428cf12897082aeca49bfa0b95e1c2958d 100644
--- a/VectoCommon/VectoCommon/Utils/SI.cs
+++ b/VectoCommon/VectoCommon/Utils/SI.cs
@@ -1085,8 +1085,7 @@ namespace TUGraz.VectoCommon.Utils
 			Denominator = new Unit[0];
 			_exponent = 1;
 
-			// check for NaN works like this: val != val
-			if (val != val) {
+			if (double.IsNaN(val)) {
 				throw new VectoException("NaN [{0}] is not allowed for SI-Values in Vecto.", GetUnitString());
 			}