diff --git a/Model/Config/Backend/TrustedForwardedIps.php b/Model/Config/Backend/TrustedForwardedIps.php
index cab8fc3..53eee10 100644
--- a/Model/Config/Backend/TrustedForwardedIps.php
+++ b/Model/Config/Backend/TrustedForwardedIps.php
@@ -78,8 +78,8 @@ public function __construct(
         TypeListInterface $cacheTypeList,
         WriterInterface $configWriter,
         Json $serializer,
-        AbstractResource $resource = null,
-        AbstractDb $resourceCollection = null,
+        ?AbstractResource $resource = null,
+        ?AbstractDb $resourceCollection = null,
         array $data = []
     ) {
         $this->configWriter = $configWriter;
diff --git a/Plugin/Config.php b/Plugin/Config.php
index 119f0f8..0ddb3f2 100644
--- a/Plugin/Config.php
+++ b/Plugin/Config.php
@@ -611,7 +611,7 @@ protected function _clearCache(
         string $memcachedDsn,
         string $redisDsn,
         Phrase $cacheLabel,
-        Phrase $preMessage = null
+        ?Phrase $preMessage = null
     ): void {
         try {
             $configs = $this->helper->getBouncerConfigs();
@@ -727,7 +727,7 @@ private function hasDsnChanged(
     private function displayCacheClearMessage(
         bool $clearCacheResult,
         Phrase $cacheLabel,
-        Phrase $preMessage = null
+        ?Phrase $preMessage = null
     ): void {
         $clearCacheMessage =
             $clearCacheResult ? __('%1 cache has been cleared.', $cacheLabel) :