diff --git a/lib/coursecatlib.php b/lib/coursecatlib.php
index 30752cea582..0faa0fbc1a0 100644
--- a/lib/coursecatlib.php
+++ b/lib/coursecatlib.php
@@ -123,7 +123,7 @@ class coursecat implements renderable, cacheable_object, IteratorAggregate {
         if (array_key_exists($name, self::$coursecatfields)) {
             if ($this->$name === false) {
                 // property was not retrieved from DB, retrieve all not retrieved fields
-                $notretrievedfields = array_diff(self::$coursecatfields, array_filter(self::$coursecatfields));
+                $notretrievedfields = array_diff_key(self::$coursecatfields, array_filter(self::$coursecatfields));
                 $record = $DB->get_record('course_categories', array('id' => $this->id),
                         join(',', array_keys($notretrievedfields)), MUST_EXIST);
                 foreach ($record as $key => $value) {
@@ -737,7 +737,7 @@ class coursecat implements renderable, cacheable_object, IteratorAggregate {
             $fields[] = 'c.summary';
             $fields[] = 'c.summaryformat';
         } else {
-            $fields[] = $DB->sql_length('c.summary'). ' hassummary';
+            $fields[] = $DB->sql_substr('c.summary', 1, 1). ' hassummary';
         }
         $sql = "SELECT ". join(',', $fields). ", $ctxselect
                 FROM {course} c
@@ -749,6 +749,9 @@ class coursecat implements renderable, cacheable_object, IteratorAggregate {
         if ($checkvisibility) {
             // Loop through all records and make sure we only return the courses accessible by user.
             foreach ($list as $course) {
+                if (isset($list[$course->id]->hassummary)) {
+                    $list[$course->id]->hassummary = strlen($list[$course->id]->hassummary) > 0;
+                }
                 if (empty($course->visible)) {
                     // load context only if we need to check capability
                     context_helper::preload_from_record($course);
diff --git a/lib/tests/coursecatlib_test.php b/lib/tests/coursecatlib_test.php
index c071edcc9ba..baa5ecde928 100644
--- a/lib/tests/coursecatlib_test.php
+++ b/lib/tests/coursecatlib_test.php
@@ -405,17 +405,25 @@ class coursecatlib_testcase extends advanced_testcase {
         // search courses
 
         // search by text
+        $res = coursecat::search_courses(array('search' => 'Test'));
+        $this->assertEquals(array($c4->id, $c3->id, $c1->id, $c8->id, $c5->id), array_keys($res));
+        $this->assertEquals(5, coursecat::search_courses_count(array('search' => 'Test')));
+
+        // search by text with specified offset and limit
+        $options = array('sort' => array('fullname' => 1), 'offset' => 1, 'limit' => 2);
+        $res = coursecat::search_courses(array('search' => 'Test'), $options);
+        $this->assertEquals(array($c4->id, $c5->id), array_keys($res));
+        $this->assertEquals(5, coursecat::search_courses_count(array('search' => 'Test'), $options));
+
+        // IMPORTANT: the tests below may fail on some databases
+        // case-insensitive search
         $res = coursecat::search_courses(array('search' => 'test'));
         $this->assertEquals(array($c4->id, $c3->id, $c1->id, $c8->id, $c5->id), array_keys($res));
         $this->assertEquals(5, coursecat::search_courses_count(array('search' => 'test')));
 
+        // non-latin language search
         $res = coursecat::search_courses(array('search' => 'Математика'));
         $this->assertEquals(array($c3->id, $c6->id), array_keys($res));
         $this->assertEquals(2, coursecat::search_courses_count(array('search' => 'Математика'), array()));
-
-        $options = array('sort' => array('fullname' => 1), 'offset' => 1, 'limit' => 2);
-        $res = coursecat::search_courses(array('search' => 'test'), $options);
-        $this->assertEquals(array($c4->id, $c5->id), array_keys($res));
-        $this->assertEquals(5, coursecat::search_courses_count(array('search' => 'test'), $options));
     }
 }
\ No newline at end of file