diff --git a/app/Config/Routing.php b/app/Config/Routing.php
index e3183d2e8db8..8d3c773157cf 100644
--- a/app/Config/Routing.php
+++ b/app/Config/Routing.php
@@ -78,7 +78,7 @@ class Routing extends BaseRouting
      * Example:
      *  public $override404 = 'App\Errors::show404';
      */
-    public $override404;
+    public ?string $override404 = null;
 
     /**
      * If TRUE, the system will attempt to match the URI against
diff --git a/system/Config/Routing.php b/system/Config/Routing.php
index 857a27769215..409bcf099f65 100644
--- a/system/Config/Routing.php
+++ b/system/Config/Routing.php
@@ -76,7 +76,7 @@ class Routing extends BaseConfig
      * Example:
      *  public $override404 = 'App\Errors::show404';
      */
-    public $override404;
+    public ?string $override404 = null;
 
     /**
      * If TRUE, the system will attempt to match the URI against
diff --git a/system/Debug/BaseExceptionHandler.php b/system/Debug/BaseExceptionHandler.php
index 576149b8bf68..9afd450e8b48 100644
--- a/system/Debug/BaseExceptionHandler.php
+++ b/system/Debug/BaseExceptionHandler.php
@@ -89,7 +89,7 @@ protected function collectVars(Throwable $exception, int $statusCode): array
      *
      * @param array|object $trace
      */
-    protected function maskSensitiveData(&$trace, array $keysToMask, string $path = '')
+    protected function maskSensitiveData(&$trace, array $keysToMask, string $path = ''): void
     {
         foreach ($keysToMask as $keyToMask) {
             $explode = explode('/', $keyToMask);
diff --git a/system/Exceptions/FrameworkException.php b/system/Exceptions/FrameworkException.php
index cee5f903e785..f268966cb6a2 100644
--- a/system/Exceptions/FrameworkException.php
+++ b/system/Exceptions/FrameworkException.php
@@ -33,6 +33,9 @@ public static function forInvalidFile(string $path)
         return new static(lang('Core.invalidFile', [$path]));
     }
 
+    /**
+     * @return static
+     */
     public static function forInvalidDirectory(string $path)
     {
         return new static(lang('Core.invalidDirectory', [$path]));
diff --git a/system/HTTP/SiteURI.php b/system/HTTP/SiteURI.php
index e64080974940..adf873bfb902 100644
--- a/system/HTTP/SiteURI.php
+++ b/system/HTTP/SiteURI.php
@@ -328,7 +328,7 @@ public function refreshPath()
     /**
      * Saves our parts from a parse_url() call.
      */
-    protected function applyParts(array $parts)
+    protected function applyParts(array $parts): void
     {
         if (! empty($parts['host'])) {
             $this->host = $parts['host'];
diff --git a/system/HotReloader/HotReloader.php b/system/HotReloader/HotReloader.php
index 2f10fae6a566..564ba544283a 100644
--- a/system/HotReloader/HotReloader.php
+++ b/system/HotReloader/HotReloader.php
@@ -16,7 +16,7 @@
  */
 final class HotReloader
 {
-    public function run()
+    public function run(): void
     {
         ini_set('zlib.output_compression', 'Off');
 
diff --git a/system/Router/AutoRouterImproved.php b/system/Router/AutoRouterImproved.php
index a186fd33ef55..6e0583d2a1e9 100644
--- a/system/Router/AutoRouterImproved.php
+++ b/system/Router/AutoRouterImproved.php
@@ -121,7 +121,7 @@ public function __construct(// @phpstan-ignore-line
         $this->controller = $this->defaultController;
     }
 
-    private function createSegments(string $uri)
+    private function createSegments(string $uri): array
     {
         $segments = explode('/', $uri);
         $segments = array_filter($segments, static fn ($segment) => $segment !== '');