diff --git a/apps/files_trashbin/lib/Trash/TrashItem.php b/apps/files_trashbin/lib/Trash/TrashItem.php
index 2ae999a20698b..70d5164747f0b 100644
--- a/apps/files_trashbin/lib/Trash/TrashItem.php
+++ b/apps/files_trashbin/lib/Trash/TrashItem.php
@@ -70,7 +70,7 @@ public function getPath() {
 		return $this->fileInfo->getPath();
 	}
 
-	public function getMimetype() {
+	public function getMimetype(): string {
 		return $this->fileInfo->getMimetype();
 	}
 
diff --git a/lib/private/Files/Cache/CacheEntry.php b/lib/private/Files/Cache/CacheEntry.php
index ab5bae316f455..c558ec7721e8f 100644
--- a/lib/private/Files/Cache/CacheEntry.php
+++ b/lib/private/Files/Cache/CacheEntry.php
@@ -65,8 +65,8 @@ public function getName() {
 	}
 
 
-	public function getMimeType() {
-		return $this->data['mimetype'];
+	public function getMimeType(): string {
+		return $this->data['mimetype'] ?? 'application/octet-stream';
 	}
 
 
diff --git a/lib/private/Files/FileInfo.php b/lib/private/Files/FileInfo.php
index 0679dc1ae7254..967d404b8a4f0 100644
--- a/lib/private/Files/FileInfo.php
+++ b/lib/private/Files/FileInfo.php
@@ -133,11 +133,8 @@ public function getId() {
 		return isset($this->data['fileid']) ? (int)$this->data['fileid'] : null;
 	}
 
-	/**
-	 * @return string
-	 */
-	public function getMimetype() {
-		return $this->data['mimetype'];
+	public function getMimetype(): string {
+		return $this->data['mimetype'] ?? 'application/octet-stream';
 	}
 
 	/**
diff --git a/lib/private/Files/Node/LazyFolder.php b/lib/private/Files/Node/LazyFolder.php
index 37b1efa0fad52..ceadc4cad1e9c 100644
--- a/lib/private/Files/Node/LazyFolder.php
+++ b/lib/private/Files/Node/LazyFolder.php
@@ -314,10 +314,7 @@ public function getUserFolder($userId) {
 		return $this->__call(__FUNCTION__, func_get_args());
 	}
 
-	/**
-	 * @inheritDoc
-	 */
-	public function getMimetype() {
+	public function getMimetype(): string {
 		if (isset($this->data['mimetype'])) {
 			return $this->data['mimetype'];
 		}
diff --git a/lib/private/Files/Node/Node.php b/lib/private/Files/Node/Node.php
index 5b8f556030c63..fd8d84883d964 100644
--- a/lib/private/Files/Node/Node.php
+++ b/lib/private/Files/Node/Node.php
@@ -339,7 +339,7 @@ public function isShared() {
 		return $this->getFileInfo(false)->isShared();
 	}
 
-	public function getMimeType() {
+	public function getMimeType(): string {
 		return $this->getFileInfo(false)->getMimetype();
 	}
 
diff --git a/lib/private/Files/Node/NonExistingFile.php b/lib/private/Files/Node/NonExistingFile.php
index 66ec2e6c0403c..7fb375b941adc 100644
--- a/lib/private/Files/Node/NonExistingFile.php
+++ b/lib/private/Files/Node/NonExistingFile.php
@@ -122,7 +122,7 @@ public function putContent($data) {
 		throw new NotFoundException();
 	}
 
-	public function getMimeType() {
+	public function getMimeType(): string {
 		if ($this->fileInfo) {
 			return parent::getMimeType();
 		} else {
diff --git a/lib/public/Files/Cache/ICacheEntry.php b/lib/public/Files/Cache/ICacheEntry.php
index 28e673071fd4c..790c972b51bfc 100644
--- a/lib/public/Files/Cache/ICacheEntry.php
+++ b/lib/public/Files/Cache/ICacheEntry.php
@@ -8,6 +8,7 @@
 namespace OCP\Files\Cache;
 
 use ArrayAccess;
+use OCP\AppFramework\Attribute\Consumable;
 
 /**
  * meta data for a file or folder
@@ -19,6 +20,7 @@
  * implemented it in the private implementation. Hence php would allow using the
  * object as array, while strictly speaking it didn't support this.
  */
+#[Consumable(since: '9.0.0')]
 interface ICacheEntry extends ArrayAccess {
 	/**
 	 * @since 9.0.0
@@ -60,10 +62,9 @@ public function getName();
 	/**
 	 * Get the full mimetype
 	 *
-	 * @return string
 	 * @since 9.0.0
 	 */
-	public function getMimeType();
+	public function getMimeType(): string;
 
 	/**
 	 * Get the first part of the mimetype
diff --git a/lib/public/Files/File.php b/lib/public/Files/File.php
index d0aceeaba3781..67b7a7d0d2ad7 100644
--- a/lib/public/Files/File.php
+++ b/lib/public/Files/File.php
@@ -10,6 +10,7 @@
 
 namespace OCP\Files;
 
+use OCP\AppFramework\Attribute\Consumable;
 use OCP\Lock\LockedException;
 
 /**
@@ -17,6 +18,7 @@
  *
  * @since 6.0.0
  */
+#[Consumable(since: '6.0.0')]
 interface File extends Node {
 	/**
 	 * Get the content of the file as string
@@ -43,10 +45,9 @@ public function putContent($data);
 	/**
 	 * Get the mimetype of the file
 	 *
-	 * @return string
 	 * @since 6.0.0
 	 */
-	public function getMimeType();
+	public function getMimeType(): string;
 
 	/**
 	 * Open the file as stream, resulting resource can be operated as stream like the result from php's own fopen
diff --git a/lib/public/Files/FileInfo.php b/lib/public/Files/FileInfo.php
index f9957f580e8e8..95419d6354ac4 100644
--- a/lib/public/Files/FileInfo.php
+++ b/lib/public/Files/FileInfo.php
@@ -7,6 +7,7 @@
  */
 namespace OCP\Files;
 
+use OCP\AppFramework\Attribute\Consumable;
 use OCP\Files\Storage\IStorage;
 
 /**
@@ -14,6 +15,7 @@
  *
  * @since 7.0.0
  */
+#[Consumable(since: '7.0.0')]
 interface FileInfo {
 	/**
 	 * @since 7.0.0
@@ -103,10 +105,9 @@ public function getPath();
 	/**
 	 * Get the full mimetype of the file or folder i.e. 'image/png'
 	 *
-	 * @return string
 	 * @since 7.0.0
 	 */
-	public function getMimetype();
+	public function getMimetype(): string;
 
 	/**
 	 * Get the first part of the mimetype of the file or folder i.e. 'image'