diff --git a/mrtest/apk_installed.py b/mrtest/apk_installed.py
index 72831a9ebffb0e1cb04b6f4a2fe78dc9159e748c..a63fe26c72dc8aad6a972e087796a10aeb81861f 100644
--- a/mrtest/apk_installed.py
+++ b/mrtest/apk_installed.py
@@ -5,11 +5,12 @@
 import logging
 import os
 import subprocess
+from typing import Optional
 
 cache_installed_all = None
 
 
-def get_installed_all():
+def get_installed_all() -> dict[str, Optional[str]]:
     global cache_installed_all
 
     if cache_installed_all: