diff --git a/lib/db/install.xml b/lib/db/install.xml
index 501b3a30678..1b86aee15e1 100644
--- a/lib/db/install.xml
+++ b/lib/db/install.xml
@@ -2363,6 +2363,9 @@
       <KEYS>
         <KEY NAME="primary" TYPE="primary" FIELDS="id" COMMENT="primary key of the table, please edit me"/>
       </KEYS>
+      <INDEXES>
+        <INDEX NAME="unreadmessageid_idx" UNIQUE="false" FIELDS="unreadmessageid" COMMENT="Index on unreadmessage id"/>
+      </INDEXES>
     </TABLE>
     <TABLE NAME="files" COMMENT="description of files, content is stored in sha1 file pool">
       <FIELDS>
diff --git a/lib/db/upgrade.php b/lib/db/upgrade.php
index e0eb87f2137..c4bbadbf64b 100644
--- a/lib/db/upgrade.php
+++ b/lib/db/upgrade.php
@@ -1990,6 +1990,7 @@ function xmldb_main_upgrade($oldversion) {
         upgrade_main_savepoint(true, 2013040300.01);
     }
 
+<<<<<<< HEAD
     if ($oldversion < 2013041200.00) {
         // MDL-29877 Some bad restores created grade items with no category information.
         $sql = "UPDATE {grade_items}
@@ -2125,5 +2126,19 @@ function xmldb_main_upgrade($oldversion) {
         upgrade_main_savepoint(true, 2013041900.00);
     }
 
+    if ($oldversion < 2013042300.00) {
+        // Adding index to unreadmessageid field of message_working table (MDL-34933)
+        $table = new xmldb_table('message_working');
+        $index = new xmldb_index('unreadmessageid_idx', XMLDB_INDEX_NOTUNIQUE, array('unreadmessageid'));
+
+        // Conditionally launch add index unreadmessageid
+        if (!$dbman->index_exists($table, $index)) {
+            $dbman->add_index($table, $index);
+        }
+
+        // Main savepoint reached.
+        upgrade_main_savepoint(true, 2013042300.00);
+    }
+
     return true;
 }
diff --git a/version.php b/version.php
index ad0b0e4da86..c037340c8e4 100644
--- a/version.php
+++ b/version.php
@@ -29,7 +29,7 @@
 
 defined('MOODLE_INTERNAL') || die();
 
-$version  = 2013042200.00;              // YYYYMMDD      = weekly release date of this DEV branch
+$version  = 2013042300.00;              // YYYYMMDD      = weekly release date of this DEV branch
                                         //         RR    = release increments - 00 in DEV branches
                                         //           .XX = incremental changes