diff --git a/sql/swad.sql b/sql/swad.sql
index 104690b5d..d7e9172d1 100644
--- a/sql/swad.sql
+++ b/sql/swad.sql
@@ -173,7 +173,7 @@ CREATE TABLE IF NOT EXISTS centres (
 -- Table chat: stored number of users in each chat room (this table is not used now)
 --
 CREATE TABLE IF NOT EXISTS chat (
-	RoomCode VARCHAR(255) NOT NULL,
+	RoomCode VARCHAR(16) NOT NULL,
 	NumUsrs INT NOT NULL,
 	UNIQUE INDEX(RoomCode));
 --
diff --git a/swad_changelog.h b/swad_changelog.h
index 7253ae0dc..326870507 100644
--- a/swad_changelog.h
+++ b/swad_changelog.h
@@ -204,13 +204,17 @@
 /****************************** Public constants *****************************/
 /*****************************************************************************/
 
-#define Log_PLATFORM_VERSION	"SWAD 16.155.1 (2017-03-09)"
+#define Log_PLATFORM_VERSION	"SWAD 16.155.2 (2017-03-09)"
 #define CSS_FILE		"swad16.147.css"
 #define JS_FILE			"swad16.144.js"
 
 // Number of lines (includes comments but not blank lines) has been got with the following command:
 // nl swad*.c swad*.h css/swad*.css py/swad*.py js/swad*.js soap/swad*?.h sql/swad*.sql | tail -1
 /*
+        Version 16.155.2: Mar 09, 2017	Adjusting size of database fields. (216596 lines)
+					1 change necessary in database:
+ALTER TABLE chat CHANGE COLUMN RoomCode RoomCode VARCHAR(16) NOT NULL;
+
         Version 16.155.1: Mar 09, 2017	Adjusting size of database fields. (216593 lines)
 					2 changes necessary in database:
 ALTER TABLE centres CHANGE COLUMN ShortName ShortName VARCHAR(511) COLLATE latin1_spanish_ci NOT NULL;
diff --git a/swad_chat.c b/swad_chat.c
index 8c52d433c..2a3a26295 100644
--- a/swad_chat.c
+++ b/swad_chat.c
@@ -51,8 +51,8 @@ extern struct Globals Gbl;
 
 #define Cht_CHAT_MAX_LEVELS 3
 
-#define Cht_MAX_CHARS_ROOM_CODE	16	// Maximum number of chars of the code of a chat room
-#define Cht_MAX_BYTES_ROOM_CODE	Cht_MAX_CHARS_ROOM_CODE
+#define Cht_MAX_CHARS_ROOM_CODE	16	// 16, maximum number of chars of the code of a chat room
+#define Cht_MAX_BYTES_ROOM_CODE	Cht_MAX_CHARS_ROOM_CODE	// 16
 
 #define Cht_MAX_CHARS_ROOM_SHRT_NAME	(128 - 1)	// 127, maximum number of chars of the short name of a chat room
 #define Cht_MAX_BYTES_ROOM_SHRT_NAME	((Cht_MAX_CHARS_ROOM_SHRT_NAME + 1) * Str_MAX_BYTES_PER_CHAR - 1)	// 2047
@@ -244,7 +244,7 @@ void Cht_ShowListOfChatRoomsWithUsrs (void)
    extern const char *Txt_Rooms_with_users;
    extern const char *Txt_CHAT_Room_code;
    extern const char *Txt_No_of_users;
-   char Query[512];
+   char Query[256];
    MYSQL_RES *mysql_res;
    MYSQL_ROW row;
    unsigned long NumRow,NumRows;
@@ -350,7 +350,7 @@ void Cht_WriteParamsRoomCodeAndNames (const char *RoomCode,const char *RoomShrtN
 
 static unsigned Cht_GetNumUsrsInChatRoom (const char *RoomCode)
   {
-   char Query[512];
+   char Query[128 + Cht_MAX_BYTES_ROOM_CODE];
    MYSQL_RES *mysql_res;
    MYSQL_ROW row;
    unsigned NumUsrs = 0;
diff --git a/swad_database.c b/swad_database.c
index 5222bc32a..f621dd758 100644
--- a/swad_database.c
+++ b/swad_database.c
@@ -443,18 +443,18 @@ mysql> DESCRIBE centres;
    /***** Table chat *****/
 /*
 mysql> DESCRIBE chat;
-+----------+--------------+------+-----+---------+-------+
-| Field    | Type         | Null | Key | Default | Extra |
-+----------+--------------+------+-----+---------+-------+
-| RoomCode | varchar(255) | NO   | PRI | NULL    |       |
-| NumUsrs  | int(11)      | NO   |     | NULL    |       |
-+----------+--------------+------+-----+---------+-------+
-2 rows in set (0.00 sec)
++----------+-------------+------+-----+---------+-------+
+| Field    | Type        | Null | Key | Default | Extra |
++----------+-------------+------+-----+---------+-------+
+| RoomCode | varchar(16) | NO   | PRI | NULL    |       |
+| NumUsrs  | int(11)     | NO   |     | NULL    |       |
++----------+-------------+------+-----+---------+-------+
+2 rows in set (0,00 sec)
 */
    DB_CreateTable ("CREATE TABLE IF NOT EXISTS chat ("\
-                   "RoomCode VARCHAR(255) NOT NULL,"
-                   "NumUsrs INT NOT NULL,"
-                   "UNIQUE INDEX(RoomCode))");
+			"RoomCode VARCHAR(16) NOT NULL,"	// Cht_MAX_BYTES_ROOM_CODE
+			"NumUsrs INT NOT NULL,"
+		   "UNIQUE INDEX(RoomCode))");
 
    /***** Table clicks_without_photo *****/
 /*