diff --git a/admin/settings/subsystems.php b/admin/settings/subsystems.php
index f2b50d5c491..81408bf3acc 100644
--- a/admin/settings/subsystems.php
+++ b/admin/settings/subsystems.php
@@ -15,8 +15,6 @@ if ($hassiteconfig) { // speedup for non-admins, add all caps used on this page
 
     $optionalsubsystems->add(new admin_setting_configcheckbox('messaging', new lang_string('messaging', 'admin'), new lang_string('configmessaging','admin'), 1));
 
-    $optionalsubsystems->add(new admin_setting_configcheckbox('messaginghidereadnotifications', new lang_string('messaginghidereadnotifications', 'admin'), new lang_string('configmessaginghidereadnotifications','admin'), 0));
-
     $options = array(DAYSECS=>new lang_string('secondstotime86400'), WEEKSECS=>new lang_string('secondstotime604800'), 2620800=>new lang_string('nummonths', 'moodle', 1), 15724800=>new lang_string('nummonths', 'moodle', 6),0=>new lang_string('never'));
     $optionalsubsystems->add(new admin_setting_configselect('messagingdeletereadnotificationsdelay', new lang_string('messagingdeletereadnotificationsdelay', 'admin'), new lang_string('configmessagingdeletereadnotificationsdelay', 'admin'), 604800, $options));
 
diff --git a/lang/en/admin.php b/lang/en/admin.php
index 740b2533b5c..72d49330780 100644
--- a/lang/en/admin.php
+++ b/lang/en/admin.php
@@ -274,7 +274,6 @@ $string['configmaxeditingtime'] = 'This specifies the amount of time people have
 $string['configmaxevents'] = 'Events to Lookahead';
 $string['configmessaging'] = 'Should the messaging system between site users be enabled?';
 $string['configmessagingallowemailoverride'] = 'Allow users to have email message notifications sent to an email address other than the email address in their profile';
-$string['configmessaginghidereadnotifications'] = 'Hide read notifications of events like forum posts when viewing messaging history';
 $string['configmessagingdeletereadnotificationsdelay'] = 'Read notifications can be deleted to save space. How long after a notification is read can it be deleted?';
 $string['configminpassworddigits'] = 'Passwords must have at least these many digits.';
 $string['configminpasswordlength'] = 'Passwords must be at least these many characters long.';
@@ -747,7 +746,6 @@ $string['mediapluginwmv'] = 'Enable .wmv filter';
 $string['mediapluginyoutube'] = 'Enable YouTube links filter';
 $string['messaging'] = 'Enable messaging system';
 $string['messagingallowemailoverride'] = 'Notification email override';
-$string['messaginghidereadnotifications'] = 'Hide read notifications';
 $string['messagingdeletereadnotificationsdelay'] = 'Delete read notifications';
 $string['minpassworddigits'] = 'Digits';
 $string['minpasswordlength'] = 'Password length';
diff --git a/lib/db/upgrade.php b/lib/db/upgrade.php
index df3883aefe8..0d8f225fcb1 100644
--- a/lib/db/upgrade.php
+++ b/lib/db/upgrade.php
@@ -2336,5 +2336,13 @@ function xmldb_main_upgrade($oldversion) {
         upgrade_main_savepoint(true, 2018091200.00);
     }
 
+    if ($oldversion < 2018091700.00) {
+        // Remove unused setting.
+        unset_config('messaginghidereadnotifications');
+
+        // Main savepoint reached.
+        upgrade_main_savepoint(true, 2018091700.00);
+    }
+
     return true;
 }
diff --git a/version.php b/version.php
index a92f3b572ca..62de152851d 100644
--- a/version.php
+++ b/version.php
@@ -29,7 +29,7 @@
 
 defined('MOODLE_INTERNAL') || die();
 
-$version  = 2018091400.00;              // YYYYMMDD      = weekly release date of this DEV branch.
+$version  = 2018091700.00;              // YYYYMMDD      = weekly release date of this DEV branch.
                                         //         RR    = release increments - 00 in DEV branches.
                                         //           .XX = incremental changes.