diff --git a/VectoCore/VectoCore/Models/Declaration/PT1.cs b/VectoCore/VectoCore/Models/Declaration/PT1.cs
index c2db9f1260ff47f17372f87697ad7bebb3ff6eb2..58ca28845c98f30a65e23e3a66f99ed18663f864 100644
--- a/VectoCore/VectoCore/Models/Declaration/PT1.cs
+++ b/VectoCore/VectoCore/Models/Declaration/PT1.cs
@@ -111,6 +111,7 @@ namespace TUGraz.VectoCore.Models.Declaration
 				_entries[index].Value, key);
 			if (pt1 < 0) {
 				pt1 = 0.SI<Second>();
+				extrapolated = true;
 				//throw new VectoException("The calculated pt1 value must not be smaller than 0. Value: " + pt1);
 			}
 			return new PT1Result() { Value = pt1, Extrapolated = extrapolated };