diff --git a/lib/ansible/modules/packaging/os/apt_key.py b/lib/ansible/modules/packaging/os/apt_key.py
index 7f07b3b3a0e..11c1ac5656b 100644
--- a/lib/ansible/modules/packaging/os/apt_key.py
+++ b/lib/ansible/modules/packaging/os/apt_key.py
@@ -26,6 +26,7 @@ notes:
     - Doesn't download the key unless it really needs it.
     - As a sanity check, downloaded key id must match the one specified.
     - Best practice is to specify the key id and the URL.
+    - Adding a new key requires an apt cache update (e.g. using the apt module's update_cache option)
 options:
     id:
         description: