diff --git a/packages/core/src/Path/FilePath.php b/packages/core/src/Path/FilePath.php
index d0aa978e0..c721019ab 100644
--- a/packages/core/src/Path/FilePath.php
+++ b/packages/core/src/Path/FilePath.php
@@ -20,6 +20,9 @@ protected function getDirectory(): DirectoryPath {
         return new DirectoryPath(dirname($this->path));
     }
 
+    /**
+     * @return ?non-empty-string
+     */
     public function getExtension(): ?string {
         $extension = pathinfo($this->path, PATHINFO_EXTENSION);
         $extension = $extension !== '' ? $extension : null;
diff --git a/packages/documentator/src/Processor/FileSystem/File.php b/packages/documentator/src/Processor/FileSystem/File.php
index 460161d88..940c348b1 100644
--- a/packages/documentator/src/Processor/FileSystem/File.php
+++ b/packages/documentator/src/Processor/FileSystem/File.php
@@ -29,6 +29,9 @@ public function __construct(
         }
     }
 
+    /**
+     * @return ?non-empty-string
+     */
     public function getExtension(): ?string {
         return $this->path->getExtension();
     }