diff --git a/source/_docs/scripts/service-calls.markdown b/source/_docs/scripts/service-calls.markdown
index 03424e8a7d6..d94130181ee 100644
--- a/source/_docs/scripts/service-calls.markdown
+++ b/source/_docs/scripts/service-calls.markdown
@@ -28,7 +28,7 @@ Instead of targeting an entity, you can also target an {% term area %} or {% ter
 This is done with the `target` key.
 
 A `target` is a map that contains at least one of the following: `area_id`, `device_id`, `entity_id`.
-Each of these can be a list.
+Each of these can be a list. The values should be lower-cased.
 
 The following example uses a single service call to turn on the lights in the
 living room area, 2 additional light devices and 2 additional light entities: