diff --git a/main/src/com/google/refine/model/Column.java b/main/src/com/google/refine/model/Column.java
index 35b554b50..e38aedb12 100644
--- a/main/src/com/google/refine/model/Column.java
+++ b/main/src/com/google/refine/model/Column.java
@@ -92,6 +92,7 @@ public class Column implements Jsonizable {
         return _reconStats;
     }
 
+    @Override
     public void write(JSONWriter writer, Properties options)
             throws JSONException {
         
@@ -154,6 +155,7 @@ public class Column implements Jsonizable {
         return column;
     }
     
+    @Override
     public String toString() {
         return _name;
     }
diff --git a/main/src/com/google/refine/model/ColumnModel.java b/main/src/com/google/refine/model/ColumnModel.java
index 5cbe61cd7..b79a0028e 100644
--- a/main/src/com/google/refine/model/ColumnModel.java
+++ b/main/src/com/google/refine/model/ColumnModel.java
@@ -156,6 +156,7 @@ public class ColumnModel implements Jsonizable {
         return _columnNames;
     }
 
+    @Override
     synchronized public void write(JSONWriter writer, Properties options)
             throws JSONException {
         
@@ -236,6 +237,7 @@ public class ColumnModel implements Jsonizable {
         
         _rootColumnGroups = new LinkedList<ColumnGroup>(columnGroups);
         Collections.sort(_rootColumnGroups, new Comparator<ColumnGroup>() {
+            @Override
             public int compare(ColumnGroup o1, ColumnGroup o2) {
                 int firstDiff = o1.startColumnIndex - o2.startColumnIndex;
                 return firstDiff != 0 ?