diff --git a/UnitsNet.Serialization.JsonNet/UnitsNetBaseJsonConverter.cs b/UnitsNet.Serialization.JsonNet/UnitsNetBaseJsonConverter.cs
index 73f4cce110..ab6549e441 100644
--- a/UnitsNet.Serialization.JsonNet/UnitsNetBaseJsonConverter.cs
+++ b/UnitsNet.Serialization.JsonNet/UnitsNetBaseJsonConverter.cs
@@ -96,7 +96,12 @@ protected IQuantity ConvertValueUnit(ValueUnit valueUnit)
 
             if (registeredQuantity is not null)
             {
-                return (IQuantity)Activator.CreateInstance(registeredQuantity, valueUnit.Value, unit)!;
+                IQuantity? instance = (IQuantity?)Activator.CreateInstance(registeredQuantity, valueUnit.Value, unit);
+                if (instance is null)
+                {
+                    throw new Exception("Unable to convert value unit, instance is null.");
+                }
+                return instance;
             }
 
             return Quantity.From(valueUnit.Value, unit);