diff --git a/installer/data/mysql/kohastructure.sql b/installer/data/mysql/kohastructure.sql
index 9e5d4367bd..eb73cc5e51 100644
--- a/installer/data/mysql/kohastructure.sql
+++ b/installer/data/mysql/kohastructure.sql
@@ -1969,7 +1969,7 @@ CREATE TABLE `serial` ( -- issues related to subscriptions
 DROP TABLE IF EXISTS sessions;
 CREATE TABLE sessions (
   `id` varchar(32) NOT NULL,
-  `a_session` text NOT NULL,
+  `a_session` mediumtext NOT NULL,
   PRIMARY KEY (`id`)
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
 
diff --git a/installer/data/mysql/updatedatabase.pl b/installer/data/mysql/updatedatabase.pl
index 0aaf114467..fcb9d28ae1 100755
--- a/installer/data/mysql/updatedatabase.pl
+++ b/installer/data/mysql/updatedatabase.pl
@@ -10183,6 +10183,15 @@ if( CheckVersion($DBversion) ) {
     SetVersion($DBversion);
 }
 
+$DBversion = "3.19.00.XXX";
+if ( CheckVersion($DBversion) ) {
+    $dbh->do(q|
+         ALTER TABLE sessions CHANGE COLUMN a_session a_session MEDIUMTEXT
+    |);
+    print "Upgrade to $DBversion done (Bug 13606: Upgrade sessions.a_session to MEDIUMTEXT)\n";
+    SetVersion($DBversion);
+}
+
 # DEVELOPER PROCESS, search for anything to execute in the db_update directory
 # SEE bug 13068
 # if there is anything in the atomicupdate, read and execute it.