diff --git a/lbplanner/classes/helpers/invite_helper.php b/lbplanner/classes/helpers/invite_helper.php
index 4cb1921b..abb50b80 100644
--- a/lbplanner/classes/helpers/invite_helper.php
+++ b/lbplanner/classes/helpers/invite_helper.php
@@ -17,6 +17,7 @@
 namespace local_lbplanner\helpers;
 
 use core_external\{external_single_structure, external_value};
+use local_lbplanner\enums\PLAN_INVITE_STATE;
 
 /**
  * Helper class for plan invites
@@ -45,4 +46,16 @@ public static function structure(): external_single_structure {
             ]
         );
     }
+
+    /**
+     * Throw error if the invite status isn't pending
+     * @param int $status the invite status
+     * @throws moodle_exception
+     */
+    public static function assert_invite_pending(int $status) {
+        if ($status !== PLAN_INVITE_STATE::PENDING) {
+            $name = PLAN_INVITE_STATE::name_from($status);
+            throw new \moodle_exception('Invite already '.$name);
+        }
+    }
 }
diff --git a/lbplanner/classes/helpers/notifications_helper.php b/lbplanner/classes/helpers/notifications_helper.php
index 3487c4c9..ac768511 100644
--- a/lbplanner/classes/helpers/notifications_helper.php
+++ b/lbplanner/classes/helpers/notifications_helper.php
@@ -59,7 +59,7 @@ public static function structure(): external_single_structure {
      * Notifies the given user about the given event, with the given info.
      *
      * @param int $userid The user to notify.
-     * @param int $info   Additional information as stringified json.
+     * @param int $info   Additional information as an integer.
      * @param int $type   The type of notification.
      *
      * @return integer The id of the notification.
diff --git a/lbplanner/classes/helpers/plan_helper.php b/lbplanner/classes/helpers/plan_helper.php
index 7f3966f4..976cf7bf 100644
--- a/lbplanner/classes/helpers/plan_helper.php
+++ b/lbplanner/classes/helpers/plan_helper.php
@@ -82,7 +82,7 @@ public static function get_owner(int $planid): int {
             'userid', ['planid' => $planid, 'accesstype' => PLAN_ACCESS_TYPE::OWNER]
         );
 
-        return $owner;
+        return intval($owner);
     }
 
     /**
diff --git a/lbplanner/services/plan/accept_invite.php b/lbplanner/services/plan/accept_invite.php
index 0b389772..2e28c200 100644
--- a/lbplanner/services/plan/accept_invite.php
+++ b/lbplanner/services/plan/accept_invite.php
@@ -20,6 +20,7 @@
 use local_lbplanner\helpers\plan_helper;
 use local_lbplanner\helpers\notifications_helper;
 use local_lbplanner\enums\{PLAN_ACCESS_TYPE, PLAN_INVITE_STATE, NOTIF_TRIGGER};
+use local_lbplanner\helpers\invite_helper;
 
 /**
  * Accept an invite to the plan.
@@ -54,23 +55,15 @@ public static function accept_invite(int $inviteid) {
         'inviteid' => $inviteid,
         ]);
 
-        if (!$DB->record_exists(plan_helper::INVITES_TABLE, ['id' => $inviteid, 'inviteeid' => $USER->id])) {
+        $invite = $DB->get_record(
+            plan_helper::INVITES_TABLE,
+            ['id' => $inviteid],
+        );
+
+        if ($invite === false) {
             throw new \moodle_exception('Invite not found');
         }
-        if (!$DB->record_exists(plan_helper::INVITES_TABLE,
-        [ 'id' => $inviteid, 'inviteeid' => $USER->id, 'status' => PLAN_INVITE_STATE::PENDING])) {
-            throw new \moodle_exception('Invite already accepted or declined');
-        }
-
-        $invite = $DB->get_record(plan_helper::INVITES_TABLE,
-        [
-            'id' => $inviteid,
-            'inviteeid' => $USER->id,
-            'status' => PLAN_INVITE_STATE::PENDING,
-        ],
-        '*',
-        MUST_EXIST
-        );
+        invite_helper::assert_invite_pending($invite->status);
 
         // Notify the user that invite has been accepted.
         notifications_helper::notify_user(
diff --git a/lbplanner/services/plan/decline_invite.php b/lbplanner/services/plan/decline_invite.php
index 1e3712ef..608b0b8b 100644
--- a/lbplanner/services/plan/decline_invite.php
+++ b/lbplanner/services/plan/decline_invite.php
@@ -17,8 +17,7 @@
 namespace local_lbplanner_services;
 
 use core_external\{external_api, external_function_parameters, external_value};
-use local_lbplanner\helpers\plan_helper;
-use local_lbplanner\helpers\notifications_helper;
+use local_lbplanner\helpers\{plan_helper, notifications_helper, invite_helper};
 use local_lbplanner\enums\{NOTIF_TRIGGER, PLAN_INVITE_STATE};
 
 /**
@@ -54,22 +53,15 @@ public static function decline_invite(int $inviteid) {
         'inviteid' => $inviteid,
         ]);
 
-        if (!$DB->record_exists(plan_helper::INVITES_TABLE, ['id' => $inviteid, 'inviteeid' => $USER->id])) {
-            throw new \moodle_exception('Invite not found');
-        }
-
-        $invite = $DB->get_record(plan_helper::INVITES_TABLE,
-        [
-            'id' => $inviteid,
-            'inviteeid' => $USER->id,
-        ],
-        '*',
-        MUST_EXIST
+        $invite = $DB->get_record(
+            plan_helper::INVITES_TABLE,
+            ['id' => $inviteid],
         );
 
-        if ($invite->status !== PLAN_INVITE_STATE::PENDING) {
-            throw new \moodle_exception('Invite already accepted or declined');
+        if ($invite === false) {
+            throw new \moodle_exception('Invite not found');
         }
+        invite_helper::assert_invite_pending($invite->status);
 
         // Notify the user that invite has been declined.
         notifications_helper::notify_user(
diff --git a/lbplanner/services/plan/invite_user.php b/lbplanner/services/plan/invite_user.php
index 9dcae19a..53714f6e 100644
--- a/lbplanner/services/plan/invite_user.php
+++ b/lbplanner/services/plan/invite_user.php
@@ -63,7 +63,7 @@ public static function invite_user(int $inviteeid): mixed {
 
         $planid = plan_helper::get_plan_id($USER->id);
 
-        if (plan_helper::get_owner($planid) !== $USER->id) {
+        if (plan_helper::get_owner($planid) !== intval($USER->id)) {
             throw new \moodle_exception('Access denied');
         }