diff --git a/completion/tests/behat/completion_other_courses.feature b/completion/tests/behat/completion_other_courses.feature
new file mode 100644
index 00000000000..66765b0954a
--- /dev/null
+++ b/completion/tests/behat/completion_other_courses.feature
@@ -0,0 +1,30 @@
+@core @core_completion
+Feature: Set completion of other courses as criteria for completion of current course
+  In order to set completion of other courses as criteria for completion of current course
+  As a user
+  I want to select the prerequisite courses in completion settings
+
+  Background:
+    Given the following "courses" exist:
+      | fullname | shortname | category | enablecompletion |
+      | Course 1 | C1        | 0        | 1                |
+      | Course 2 | C2        | 0        | 1                |
+    And the following "users" exist:
+      | username | firstname | lastname | email                |
+      | student1 | Student   | One      | student1@example.com |
+    And the following "course enrolments" exist:
+      | user     | course | role    |
+      | student1 | C1     | student |
+
+  @javascript
+  Scenario: Set completion of prerequisite course as completion criteria of current course
+    When I log in as "admin"
+    And I am on "Course 1" course homepage with editing mode on
+    And I navigate to "Course completion" in current page administration
+    And I click on "Condition: Completion of other courses" "link"
+    And I set the field "Courses available" to "Course 2"
+    And I press "Save changes"
+    And I add the "Course completion status" block
+    And I click on "View course report" "link" in the "Course completion status" "block"
+    Then I should see "Course 2" in the "completion-progress" "table"
+    And I should see "Student One" in the "completion-progress" "table"
diff --git a/course/completion_form.php b/course/completion_form.php
index f8501011c90..937a0eee150 100644
--- a/course/completion_form.php
+++ b/course/completion_form.php
@@ -128,14 +128,16 @@ class course_completion_form extends moodleform {
         }
 
         // Get applicable courses (prerequisites).
-        $selectedcourses = $DB->get_fieldset_sql("SELECT cc.courseinstance
-                  FROM {course_completion_criteria} cc WHERE cc.course = ?", [$course->id]);
         $hasselectablecourses = core_course_category::search_courses(['onlywithcompletion' => true], ['limit' => 2]);
         unset($hasselectablecourses[$course->id]);
         if ($hasselectablecourses) {
             // Show multiselect box.
             $mform->addElement('course', 'criteria_course', get_string('coursesavailable', 'completion'),
                 array('multiple' => 'multiple', 'onlywithcompletion' => true, 'exclude' => $course->id));
+            $mform->setType('criteria_course', PARAM_INT);
+
+            $selectedcourses = $DB->get_fieldset_select('course_completion_criteria', 'courseinstance',
+                'course = :course AND criteriatype = :type', ['course' => $course->id, 'type' => COMPLETION_CRITERIA_TYPE_COURSE]);
             $mform->setDefault('criteria_course', $selectedcourses);
 
             // Map aggregation methods to context-sensitive human readable dropdown menu.
diff --git a/lib/db/upgrade.php b/lib/db/upgrade.php
index dcc2f48034a..1df218e4e64 100644
--- a/lib/db/upgrade.php
+++ b/lib/db/upgrade.php
@@ -2486,5 +2486,16 @@ function xmldb_main_upgrade($oldversion) {
         upgrade_main_savepoint(true, 2020061500.02);
     }
 
+    if ($oldversion < 2020061501.01) {
+        // Clean up completion criteria records referring to NULL course prerequisites.
+        $select = 'criteriatype = :type AND courseinstance IS NULL';
+        $params = ['type' => 8]; // COMPLETION_CRITERIA_TYPE_COURSE.
+
+        $DB->delete_records_select('course_completion_criteria', $select, $params);
+
+        // Main savepoint reached.
+        upgrade_main_savepoint(true, 2020061501.01);
+    }
+
     return true;
 }
diff --git a/version.php b/version.php
index d84e55c6998..f7cc1973cae 100644
--- a/version.php
+++ b/version.php
@@ -29,7 +29,7 @@
 
 defined('MOODLE_INTERNAL') || die();
 
-$version  = 2020061501.00;              // 20200615      = branching date YYYYMMDD - do not modify!
+$version  = 2020061501.01;              // 20200615      = branching date YYYYMMDD - do not modify!
                                         //         RR    = release increments - 00 in DEV branches.
                                         //           .XX = incremental changes.
 $release  = '3.9.1 (Build: 20200713)'; // Human-friendly version name