diff --git a/docs/configuration/recording_rules.md b/docs/configuration/recording_rules.md
index 78aa0cec77..4cf801b97f 100644
--- a/docs/configuration/recording_rules.md
+++ b/docs/configuration/recording_rules.md
@@ -45,7 +45,8 @@ dashboards, which need to query the same expression repeatedly every time they
 refresh.
 
 Recording and alerting rules exist in a rule group. Rules within a group are
-run sequentially at a regular interval.
+run sequentially at a regular interval. The names of recording and alerting rules
+must be [valid metric names](https://prometheus.io/docs/concepts/data_model/#metric-names-and-labels).
 
 The syntax of a rule file is: