diff --git a/java/com.sap.sailing.domain.common/src/com/sap/sailing/domain/common/dto/PreviousCompetitorDTOImpl.java b/java/com.sap.sailing.domain.common/src/com/sap/sailing/domain/common/dto/PreviousCompetitorDTOImpl.java
index ceb88478fe1..fe3c46b0a87 100755
--- a/java/com.sap.sailing.domain.common/src/com/sap/sailing/domain/common/dto/PreviousCompetitorDTOImpl.java
+++ b/java/com.sap.sailing.domain.common/src/com/sap/sailing/domain/common/dto/PreviousCompetitorDTOImpl.java
@@ -170,4 +170,10 @@ public class PreviousCompetitorDTOImpl implements CompetitorWithBoatDTO {
     public CompetitorWithBoatDTO getCompetitorFromPrevious(LeaderboardDTO previousVersion) {
         return previousVersion.competitors.get(indexInPreviousCompetitorList);
     }
+
+    @Override
+    public boolean hasBoat() {
+        throw new RuntimeException("Internal error. Objects of type "+PreviousCompetitorDTOImpl.class.getName()+
+                " need to be replaced by an object of "+CompetitorWithBoatDTOImpl.class.getName()+" after deserialization");
+    }
 }
\ No newline at end of file
diff --git a/java/com.sap.sailing.gwt.ui/src/main/java/com/sap/sailing/gwt/ui/adminconsole/CompetitorToBoatMappingsViewPanel.java b/java/com.sap.sailing.gwt.ui/src/main/java/com/sap/sailing/gwt/ui/adminconsole/CompetitorToBoatMappingsViewPanel.java
index e1d808b19fb..26fe2c02786 100644
--- a/java/com.sap.sailing.gwt.ui/src/main/java/com/sap/sailing/gwt/ui/adminconsole/CompetitorToBoatMappingsViewPanel.java
+++ b/java/com.sap.sailing.gwt.ui/src/main/java/com/sap/sailing/gwt/ui/adminconsole/CompetitorToBoatMappingsViewPanel.java
@@ -67,7 +67,7 @@ public class CompetitorToBoatMappingsViewPanel extends SimplePanel {
         HorizontalPanel buttonPanel = new HorizontalPanel();
         buttonPanel.setSpacing(5);
         mainPanel.add(buttonPanel);
-        Grid grid = new Grid(1,2);
+        Grid grid = new Grid(1, 2);
         grid.setWidget(0, 0, competitorsPanel);
         grid.setWidget(0, 1, boatsPanel);
         grid.getCellFormatter().setVerticalAlignment(0, 0, HasVerticalAlignment.ALIGN_TOP);