diff --git a/docs/tags.md b/docs/tags.md
index f0e481a..3bf059e 100644
--- a/docs/tags.md
+++ b/docs/tags.md
@@ -28,3 +28,5 @@ These additional tags apply to groups of tags. See `scripts/schema/topics.yaml`
 | `porn` | Any kind of pornagraphic content.
 | `nsfl` | `gore` + `high_risk`
 | `nsfw` | `porn` + `nsfl`
+
+*In `topics.yaml`, a topic which references another topic MUST be below the referenced topic. Otherwise it may not be properly resolved.*