diff --git a/src/main/java/org/sadtech/autoresponder/Autoresponder.java b/src/main/java/org/sadtech/autoresponder/Autoresponder.java
index 80b104f..a269541 100644
--- a/src/main/java/org/sadtech/autoresponder/Autoresponder.java
+++ b/src/main/java/org/sadtech/autoresponder/Autoresponder.java
@@ -53,7 +53,7 @@ public class Autoresponder {
         } catch (NotFoundUnitException e) {
             unit = defaultUnit;
         }
-        return unit;
+        return Optional.ofNullable(unit).orElseThrow(NotFoundUnitException::new);
     }
 
     private Unit nextUnit(Set<Unit> nextUnits, String message) {