diff --git a/src/Compatibility/ContentReviewCompatability.php b/src/Compatibility/ContentReviewCompatability.php
index ed5a0c8..a088946 100644
--- a/src/Compatibility/ContentReviewCompatability.php
+++ b/src/Compatibility/ContentReviewCompatability.php
@@ -24,11 +24,11 @@ class ContentReviewCompatability
     public static function start()
     {
         $compatibility = [
-            self::SUBSITES => null,
+            ContentReviewCompatability::SUBSITES => null,
         ];
 
         if (ClassInfo::exists(Subsite::class)) {
-            $compatibility[self::SUBSITES] = Subsite::$disable_subsite_filter;
+            $compatibility[ContentReviewCompatability::SUBSITES] = Subsite::$disable_subsite_filter;
             Subsite::disable_subsite_filter(true);
         }
 
@@ -41,7 +41,7 @@ public static function start()
     public static function done(array $compatibility)
     {
         if (class_exists(Subsite::class)) {
-            Subsite::$disable_subsite_filter = $compatibility[self::SUBSITES];
+            Subsite::$disable_subsite_filter = $compatibility[ContentReviewCompatability::SUBSITES];
         }
     }
 }
diff --git a/src/Extensions/SiteTreeContentReview.php b/src/Extensions/SiteTreeContentReview.php
index 2e00dd4..f5fca23 100644
--- a/src/Extensions/SiteTreeContentReview.php
+++ b/src/Extensions/SiteTreeContentReview.php
@@ -335,7 +335,7 @@ public function updateSettingsFields(FieldList $fields)
         Requirements::javascript('silverstripe/contentreview:client/dist/js/contentreview.js');
         // Display read-only version only
         if (!Permission::check("EDIT_CONTENT_REVIEW_FIELDS")) {
-            $schedule = self::get_schedule();
+            $schedule = SiteTreeContentReview::get_schedule();
             $contentOwners = ReadonlyField::create(
                 "ROContentOwners",
                 _t(__CLASS__ . ".CONTENTOWNERS", "Content Owners"),
@@ -429,7 +429,7 @@ public function updateSettingsFields(FieldList $fields)
         $reviewFrequency = DropdownField::create(
             "ReviewPeriodDays",
             _t(__CLASS__ . ".REVIEWFREQUENCY", "Review frequency"),
-            self::get_schedule()
+            SiteTreeContentReview::get_schedule()
         )
             ->addExtraClass('custom-setting')
             ->setDescription(_t(