diff --git a/src/main/java/de/deadlocker8/budgetmaster/database/model/v4/BackupDatabase_v4.java b/src/main/java/de/deadlocker8/budgetmaster/database/model/v4/BackupDatabase_v4.java
index f5d408500c1a19de878206ff8ad0388af7d26c91..034f3717b53b8ccf9f7f53b1341f9988d5e8dd80 100644
--- a/src/main/java/de/deadlocker8/budgetmaster/database/model/v4/BackupDatabase_v4.java
+++ b/src/main/java/de/deadlocker8/budgetmaster/database/model/v4/BackupDatabase_v4.java
@@ -108,6 +108,6 @@ public class BackupDatabase_v4 implements BackupDatabase
 	@Override
 	public InternalDatabase convertToInternal()
 	{
-		return null;
+		throw new UnsupportedOperationException();
 	}
 }
diff --git a/src/main/java/de/deadlocker8/budgetmaster/database/model/v5/BackupDatabase_v5.java b/src/main/java/de/deadlocker8/budgetmaster/database/model/v5/BackupDatabase_v5.java
index 6e8700a52636026fc8b6f56ac823c4398d02f63b..de8c6985aa011c3e10221819982533c14fa7a3b4 100644
--- a/src/main/java/de/deadlocker8/budgetmaster/database/model/v5/BackupDatabase_v5.java
+++ b/src/main/java/de/deadlocker8/budgetmaster/database/model/v5/BackupDatabase_v5.java
@@ -136,7 +136,7 @@ public class BackupDatabase_v5 implements BackupDatabase
 	@Override
 	public BackupDatabase upgrade()
 	{
-		return null;
+		throw new UnsupportedOperationException();
 	}
 
 	public static BackupDatabase_v5 createFromInternalEntities(InternalDatabase database)