diff --git a/group/group_form.php b/group/group_form.php
index 72e6849fa40..a7f15564fca 100644
--- a/group/group_form.php
+++ b/group/group_form.php
@@ -111,11 +111,19 @@ class group_form extends moodleform {
                 }
             }
 
-            if (!empty($CFG->groupenrolmentkeypolicy) and $data['enrolmentkey'] != '' and $group->enrolmentkey !== $data['enrolmentkey']) {
-                // enforce password policy only if changing password
+            if ($data['enrolmentkey'] != '') {
                 $errmsg = '';
-                if (!check_password_policy($data['enrolmentkey'], $errmsg)) {
+                if (!empty($CFG->groupenrolmentkeypolicy) && $group->enrolmentkey !== $data['enrolmentkey']
+                        && !check_password_policy($data['enrolmentkey'], $errmsg)) {
+                    // Enforce password policy when the password is changed.
                     $errors['enrolmentkey'] = $errmsg;
+                } else {
+                    // Prevent twice the same enrolment key in course groups.
+                    $sql = "SELECT id FROM {groups} WHERE id <> :groupid AND courseid = :courseid AND enrolmentkey = :key";
+                    $params = array('groupid' => $data['id'], 'courseid' => $COURSE->id, 'key' => $data['enrolmentkey']);
+                    if ($DB->record_exists_sql($sql, $params)) {
+                        $errors['enrolmentkey'] = get_string('enrolmentkeyalreadyinuse', 'group');
+                    }
                 }
             }
 
@@ -123,6 +131,11 @@ class group_form extends moodleform {
             $errors['name'] = get_string('groupnameexists', 'group', $name);
         } else if (!empty($idnumber) && groups_get_group_by_idnumber($COURSE->id, $idnumber)) {
             $errors['idnumber']= get_string('idnumbertaken');
+        } else if ($data['enrolmentkey'] != '') {
+            // Prevent the same enrolment key from being used multiple times in course groups.
+            if ($DB->record_exists('groups', array('courseid' => $COURSE->id, 'enrolmentkey' => $data['enrolmentkey']))) {
+                $errors['enrolmentkey'] = get_string('enrolmentkeyalreadyinuse', 'group');
+            }
         }
 
         return $errors;
diff --git a/group/tests/behat/create_groups.feature b/group/tests/behat/create_groups.feature
index 51970edc5ab..505b59748a9 100644
--- a/group/tests/behat/create_groups.feature
+++ b/group/tests/behat/create_groups.feature
@@ -89,3 +89,37 @@ Feature: Organize students into groups
       | Grouping name | Not the greatest grouping, but it's ok! |
     And I press "Save changes"
     And I should see "Not the greatest grouping, but it's ok!"
+
+  Scenario: Create groups with enrolment key
+    Given the following "courses" exist:
+      | fullname | shortname | category | groupmode |
+      | Course 1 | C1 | 0 | 1 |
+      | Course 2 | C2 | 0 | 1 |
+    And I log in as "admin"
+    And I follow "Course 1"
+    And I expand "Users" node
+    And I follow "Groups"
+    When I press "Create group"
+    And I set the following fields to these values:
+      | Group name | Group A |
+      | Enrolment key | Abcdef-1 |
+    And I press "Save changes"
+    And I press "Create group"
+    And I set the following fields to these values:
+      | Group name | Group B |
+      | Enrolment key | Abcdef-1 |
+    And I press "Save changes"
+    Then I should see "This enrolment key is already used for another group."
+    And I set the following fields to these values:
+      | Enrolment key | Abcdef-2 |
+    And I press "Save changes"
+    And the "groups" select box should contain "Group B (0)"
+    And I am on homepage
+    And I follow "Course 2"
+    And I expand "Users" node
+    And I follow "Groups"
+    And I press "Create group"
+    And I set the following fields to these values:
+      | Group name | Group A |
+      | Enrolment key | Abcdef-1 |
+    And I should not see "This enrolment key is already used for another group."
\ No newline at end of file
diff --git a/group/tests/behat/update_groups.feature b/group/tests/behat/update_groups.feature
index a363d2bb0a8..66e19206768 100644
--- a/group/tests/behat/update_groups.feature
+++ b/group/tests/behat/update_groups.feature
@@ -100,3 +100,54 @@ Feature: Automatic updating of groups and groupings
     And the "idnumber" "field" should be readonly
     And the field "idnumber" matches value "An ID"
 
+  @javascript
+  Scenario: Update groups with enrolment key
+    Given the following "courses" exist:
+      | fullname | shortname |
+      | Course 2 | C2 |
+    And the following "course enrolments" exist:
+      | user | course | role |
+      | teacher1 | C2 | editingteacher |
+    And I log out
+    And I log in as "teacher1"
+    And I follow "Course 1"
+    And I expand "Users" node
+    And I follow "Groups"
+    And I set the field "groups" to "Group (with ID)"
+    And I press "Edit group settings"
+    And I set the following fields to these values:
+      | Enrolment key | badpasswd |
+    When I press "Save changes"
+    Then I should see "Passwords must have at least 1 digit(s)"
+    And I set the following fields to these values:
+      | Enrolment key | Abcdef-1 |
+    And I press "Save changes"
+    And I set the field "groups" to "Group (with ID)"
+    And I press "Edit group settings"
+    And I press "Save changes"
+    And I should not see "This enrolment key is already used for another group."
+    And I set the field "groups" to "Group (without ID)"
+    And I press "Edit group settings"
+    And I set the following fields to these values:
+      | Enrolment key | Abcdef-1 |
+    And I press "Save changes"
+    And I should see "This enrolment key is already used for another group."
+    And I set the following fields to these values:
+      | Enrolment key | Abcdef-2 |
+    And I press "Save changes"
+    And I should not see "This enrolment key is already used for another group."
+    And I am on homepage
+    And I follow "Course 2"
+    And I expand "Users" node
+    And I follow "Groups"
+    And I press "Create group"
+    And I set the following fields to these values:
+      | Group name | Group A |
+    And I press "Save changes"
+    And I should not see "This enrolment key is already used for another group."
+    And I set the field "groups" to "Group A"
+    And I press "Edit group settings"
+    And I set the following fields to these values:
+      | Enrolment key | Abcdef-1 |
+    And I press "Save changes"
+    And I should not see "This enrolment key is already used for another group."
\ No newline at end of file
diff --git a/lang/en/group.php b/lang/en/group.php
index 7fee0f78d63..ac1316a1f9d 100644
--- a/lang/en/group.php
+++ b/lang/en/group.php
@@ -61,6 +61,7 @@ $string['enrolmentkey'] = 'Enrolment key';
 $string['enrolmentkey_help'] = 'An enrolment key enables access to the course to be restricted to only those who know the key. If a group enrolment key is specified, then not only will entering that key let the user into the course, but it will also automatically make them a member of this group.
 
 Note: Group enrolment keys must be enabled in the self enrolment settings and an enrolment key for the course must also be specified.';
+$string['enrolmentkeyalreadyinuse'] = 'This enrolment key is already used for another group.';
 $string['erroraddremoveuser'] = 'Error adding/removing user {$a} to group';
 $string['erroreditgroup'] = 'Error creating/updating group {$a}';
 $string['erroreditgrouping'] = 'Error creating/updating grouping {$a}';