diff --git a/course/format/lib.php b/course/format/lib.php
index b51d77dbb3c..33b9f553f18 100644
--- a/course/format/lib.php
+++ b/course/format/lib.php
@@ -109,6 +109,11 @@ abstract class format_base {
             return self::$classesforformat[$format];
         }
 
+        if (PHPUNIT_TEST && class_exists('format_' . $format)) {
+            // Allow unittests to use non-existing course formats.
+            return $format;
+        }
+
         // Else return default format
         $defaultformat = get_config('moodlecourse', 'format');
         if (!in_array($defaultformat, $plugins)) {
@@ -136,7 +141,7 @@ abstract class format_base {
         if (!isset($classnames[$format])) {
             $plugins = core_component::get_plugin_list('format');
             $usedformat = self::get_format_or_default($format);
-            if (file_exists($plugins[$usedformat].'/lib.php')) {
+            if (isset($plugins[$usedformat]) && file_exists($plugins[$usedformat].'/lib.php')) {
                 require_once($plugins[$usedformat].'/lib.php');
             }
             $classnames[$format] = 'format_'. $usedformat;
@@ -906,6 +911,29 @@ abstract class format_base {
         }
         return ($sectionnum && ($course = $this->get_course()) && $course->marker == $sectionnum);
     }
+
+    /**
+     * Allows to specify for modinfo that section is not available even when it is visible and conditionally available.
+     *
+     * Note: affected user can be retrieved as: $section->modinfo->userid
+     *
+     * Course format plugins can override the method to change the properties $available and $availableinfo that were
+     * calculated by conditional availability.
+     * To make section unavailable set:
+     *     $available = false;
+     * To make unavailable section completely hidden set:
+     *     $availableinfo = '';
+     * To make unavailable section visible with availability message set:
+     *     $availableinfo = get_string('sectionhidden', 'format_xxx');
+     *
+     * @param section_info $section
+     * @param bool $available the 'available' propery of the section_info as it was evaluated by conditional availability.
+     *     Can be changed by the method but 'false' can not be overridden by 'true'.
+     * @param string $availableinfo the 'availableinfo' propery of the section_info as it was evaluated by conditional availability.
+     *     Can be changed by the method
+     */
+    public function section_get_available_hook(section_info $section, &$available, &$availableinfo) {
+    }
 }
 
 /**
diff --git a/course/format/upgrade.txt b/course/format/upgrade.txt
index 1eed444c7f2..79168540e32 100644
--- a/course/format/upgrade.txt
+++ b/course/format/upgrade.txt
@@ -7,6 +7,7 @@ Overview of this plugin type at http://docs.moodle.org/dev/Course_formats
   to determine the section selector, rather than a hard-coded `li.section`.
 * Activity duplication in /course/modduplicate.php is deprecated and is now done in /course/mod.php.  Deprecated calls will be honored by
   redirecting to /course/mod.php for 3rd party plugin support.
+* New method format_base::section_get_available_hook() allows plugins to override section availability.
 
 === 2.7 ===
 * The ->testedbrowsers array no longer needs to be defined in supports_ajax().
diff --git a/course/tests/courseformat_test.php b/course/tests/courseformat_test.php
new file mode 100644
index 00000000000..c7529cb9c24
--- /dev/null
+++ b/course/tests/courseformat_test.php
@@ -0,0 +1,104 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Course related unit tests
+ *
+ * @package    core_course
+ * @copyright  2014 Marina Glancy
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+defined('MOODLE_INTERNAL') || die();
+
+global $CFG;
+require_once($CFG->dirroot . '/course/lib.php');
+require_once($CFG->dirroot . '/course/tests/fixtures/format_theunittest.php');
+
+class core_course_courseformat_testcase extends advanced_testcase {
+    public function test_available_hook() {
+        global $DB;
+        $this->resetAfterTest();
+
+        // Generate a course with two sections (0 and 1) and two modules. Course format is set to 'theunittest'.
+        $generator = $this->getDataGenerator();
+        $course1 = $generator->create_course(array('format' => 'theunittest'));
+        $this->assertEquals('theunittest', $course1->format);
+        course_create_sections_if_missing($course1, array(0, 1));
+        $assign0 = $generator->create_module('assign', array('course' => $course1, 'section' => 0));
+        $assign1 = $generator->create_module('assign', array('course' => $course1, 'section' => 1));
+
+        // Enrol student and teacher.
+        $roleids = $DB->get_records_menu('role', null, '', 'shortname, id');
+        $student = $generator->create_user();
+        $generator->enrol_user($student->id, $course1->id, $roleids['student']);
+        $teacher = $generator->create_user();
+        $generator->enrol_user($teacher->id, $course1->id, $roleids['editingteacher']);
+
+        // Make sure that initially both sections and both modules are available and visible for a student.
+        $modinfostudent = get_fast_modinfo($course1, $student->id);
+        $this->assertTrue($modinfostudent->get_section_info(1)->available);
+        $this->assertTrue($modinfostudent->get_cm($assign0->cmid)->available);
+        $this->assertTrue($modinfostudent->get_cm($assign0->cmid)->uservisible);
+        $this->assertTrue($modinfostudent->get_cm($assign1->cmid)->available);
+        $this->assertTrue($modinfostudent->get_cm($assign1->cmid)->uservisible);
+
+        // Set 'hideoddsections' for the course to 1.
+        // Section1 and assign1 will be unavailable, uservisible will be false for student and true for teacher.
+        $data = (object)array('id' => $course1->id, 'hideoddsections' => 1);
+        course_get_format($course1)->update_course_format_options($data);
+        $modinfostudent = get_fast_modinfo($course1, $student->id);
+        $this->assertFalse($modinfostudent->get_section_info(1)->available);
+        $this->assertEmpty($modinfostudent->get_section_info(1)->availableinfo);
+        $this->assertFalse($modinfostudent->get_section_info(1)->uservisible);
+        $this->assertTrue($modinfostudent->get_cm($assign0->cmid)->available);
+        $this->assertTrue($modinfostudent->get_cm($assign0->cmid)->uservisible);
+        $this->assertFalse($modinfostudent->get_cm($assign1->cmid)->available);
+        $this->assertFalse($modinfostudent->get_cm($assign1->cmid)->uservisible);
+
+        $modinfoteacher = get_fast_modinfo($course1, $teacher->id);
+        $this->assertFalse($modinfoteacher->get_section_info(1)->available);
+        $this->assertEmpty($modinfoteacher->get_section_info(1)->availableinfo);
+        $this->assertTrue($modinfoteacher->get_section_info(1)->uservisible);
+        $this->assertTrue($modinfoteacher->get_cm($assign0->cmid)->available);
+        $this->assertTrue($modinfoteacher->get_cm($assign0->cmid)->uservisible);
+        $this->assertFalse($modinfoteacher->get_cm($assign1->cmid)->available);
+        $this->assertTrue($modinfoteacher->get_cm($assign1->cmid)->uservisible);
+
+        // Set 'hideoddsections' for the course to 2.
+        // Section1 and assign1 will be unavailable, uservisible will be false for student and true for teacher.
+        // Property availableinfo will be not empty.
+        $data = (object)array('id' => $course1->id, 'hideoddsections' => 2);
+        course_get_format($course1)->update_course_format_options($data);
+        $modinfostudent = get_fast_modinfo($course1, $student->id);
+        $this->assertFalse($modinfostudent->get_section_info(1)->available);
+        $this->assertNotEmpty($modinfostudent->get_section_info(1)->availableinfo);
+        $this->assertFalse($modinfostudent->get_section_info(1)->uservisible);
+        $this->assertTrue($modinfostudent->get_cm($assign0->cmid)->available);
+        $this->assertTrue($modinfostudent->get_cm($assign0->cmid)->uservisible);
+        $this->assertFalse($modinfostudent->get_cm($assign1->cmid)->available);
+        $this->assertFalse($modinfostudent->get_cm($assign1->cmid)->uservisible);
+
+        $modinfoteacher = get_fast_modinfo($course1, $teacher->id);
+        $this->assertFalse($modinfoteacher->get_section_info(1)->available);
+        $this->assertNotEmpty($modinfoteacher->get_section_info(1)->availableinfo);
+        $this->assertTrue($modinfoteacher->get_section_info(1)->uservisible);
+        $this->assertTrue($modinfoteacher->get_cm($assign0->cmid)->available);
+        $this->assertTrue($modinfoteacher->get_cm($assign0->cmid)->uservisible);
+        $this->assertFalse($modinfoteacher->get_cm($assign1->cmid)->available);
+        $this->assertTrue($modinfoteacher->get_cm($assign1->cmid)->uservisible);
+    }
+}
diff --git a/course/tests/fixtures/format_theunittest.php b/course/tests/fixtures/format_theunittest.php
new file mode 100644
index 00000000000..b53dfd872d0
--- /dev/null
+++ b/course/tests/fixtures/format_theunittest.php
@@ -0,0 +1,81 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+defined('MOODLE_INTERNAL') || die();
+
+require_once($CFG->dirroot . '/course/format/lib.php');
+
+/**
+ * Fixture for fake course format testing course format API.
+ *
+ * @package    core_course
+ * @copyright  2014 Marina Glancy
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class format_theunittest extends format_base {
+
+    /**
+     * Definitions of the additional options that format uses
+     *
+     * @param bool $foreditform
+     * @return array of options
+     */
+    public function course_format_options($foreditform = false) {
+        static $courseformatoptions = false;
+        if ($courseformatoptions === false) {
+            $courseformatoptions = array(
+                'hideoddsections' => array(
+                    'default' => 0,
+                    'type' => PARAM_INT,
+                ),
+            );
+        }
+        if ($foreditform && !isset($courseformatoptions['hideoddsections']['label'])) {
+            $sectionmenu = array(
+                0 => 'Never',
+                1 => 'Hide without notice',
+                2 => 'Hide with notice'
+            );
+            $courseformatoptionsedit = array(
+                'hideoddsections' => array(
+                    'label' => 'Hide odd sections',
+                    'element_type' => 'select',
+                    'element_attributes' => array($sectionmenu),
+                ),
+            );
+            $courseformatoptions = array_merge_recursive($courseformatoptions, $courseformatoptionsedit);
+        }
+        return $courseformatoptions;
+    }
+
+    /**
+     * Allows to specify for modinfo that section is not available even when it is visible and conditionally available.
+     *
+     * @param section_info $section
+     * @param bool $available
+     * @param string $availableinfo
+     */
+    public function section_get_available_hook(section_info $section, &$available, &$availableinfo) {
+        if (($section->section % 2) && ($hideoddsections = $this->get_course()->hideoddsections)) {
+            $available = false;
+            if ($hideoddsections == 2) {
+                $availableinfo = 'Odd sections are oddly hidden';
+            } else {
+                $availableinfo = '';
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/lib/modinfolib.php b/lib/modinfolib.php
index 13380a5ce5e..6576123b4b1 100644
--- a/lib/modinfolib.php
+++ b/lib/modinfolib.php
@@ -1791,8 +1791,12 @@ class cm_info implements IteratorAggregate {
             // but we know that this function does not need anything more than basic data.
             $this->available = $ci->is_available($this->availableinfo, true,
                     $userid, $this->modinfo);
+        } else {
+            $this->available = true;
+        }
 
-            // Check parent section
+        // Check parent section.
+        if ($this->available) {
             $parentsection = $this->modinfo->get_section_info($this->sectionnum);
             if (!$parentsection->available) {
                 // Do not store info from section here, as that is already
@@ -1800,11 +1804,9 @@ class cm_info implements IteratorAggregate {
                 // the flag
                 $this->available = false;
             }
-        } else {
-            $this->available = true;
         }
 
-        // Update visible state for current user
+        // Update visible state for current user.
         $this->update_user_visible();
 
         // Let module make dynamic changes at this point
@@ -2678,15 +2680,22 @@ class section_info implements IteratorAggregate {
             // Has already been calculated or does not need calculation.
             return $this->_available;
         }
+        $this->_available = true;
+        $this->_availableinfo = '';
         if (!empty($CFG->enableavailability)) {
             require_once($CFG->libdir. '/conditionlib.php');
             // Get availability information.
             $ci = new \core_availability\info_section($this);
             $this->_available = $ci->is_available($this->_availableinfo, true,
                     $userid, $this->modinfo);
-        } else {
-            $this->_available = true;
-            $this->_availableinfo = '';
+        }
+        // Execute the hook from the course format that may override the available/availableinfo properties.
+        $currentavailable = $this->_available;
+        course_get_format($this->modinfo->get_course())->
+            section_get_available_hook($this, $this->_available, $this->_availableinfo);
+        if (!$currentavailable && $this->_available) {
+            debugging('section_get_available_hook() can not make unavailable section available', DEBUG_DEVELOPER);
+            $this->_available = $currentavailable;
         }
         return $this->_available;
     }