diff --git a/core/src/cz/nic/tablexia/model/game/GameDAO.java b/core/src/cz/nic/tablexia/model/game/GameDAO.java
index 43bd4f7b46a5c11e7b5b4bfbef4b12886538af4d..b37264f0722f6c80bd433a4cf9fb8bfd249aa3a8 100644
--- a/core/src/cz/nic/tablexia/model/game/GameDAO.java
+++ b/core/src/cz/nic/tablexia/model/game/GameDAO.java
@@ -166,7 +166,7 @@ public class GameDAO {
     public static final String GAME_SELECT_FOR_RANK_MANAGER = "SELECT id, difficulty_number, game_number, start_time, end_time FROM game WHERE user_id = ? AND end_time IS NOT NULL AND end_time != 0 ORDER BY end_time ASC";
 
     // classic statements
-    public static final String IMPORT_GAME_INSERT = "INSERT INTO game (user_id, difficulty_number, game_number, random_seed, start_time, end_time, sync_at) VALUES (%d, %d, %d, %d, %d, %d, %d)";
+    public static final String IMPORT_GAME_INSERT = "INSERT INTO game (user_id, difficulty_number, game_number, random_seed, start_time, end_time, sync_at) VALUES (%d, %d, %d, %d, %d, %s, %d)";
 
 
     private static Long insertNewGame(User user, GameDifficulty difficulty, GameDefinition gameDefinition, TablexiaRandom random) {
@@ -212,7 +212,9 @@ public class GameDAO {
         try {
             Long gameId = null;
             Statement st = TablexiaStorage.getInstance().createStatement();
-            String sql = String.format(IMPORT_GAME_INSERT, user.getId(), difficulty, gameNumber, randomSeed, startTime, endTime, System.currentTimeMillis());
+            // workaround for sync error -> serialized JSON from server contains 0 instead of NULL
+//            String sql = String.format(IMPORT_GAME_INSERT, user.getId(), difficulty, gameNumber, randomSeed, startTime, endTime, System.currentTimeMillis());
+            String sql = String.format(IMPORT_GAME_INSERT, user.getId(), difficulty, gameNumber, randomSeed, startTime, endTime != 0 ? String.valueOf(endTime) : "NULL", System.currentTimeMillis());
             st.executeUpdate(sql);
             gameId = selectLastGameId();
             st.close();