diff --git a/docs/command-line/promtool.md b/docs/command-line/promtool.md
index 59c46dd79..6784fb99f 100644
--- a/docs/command-line/promtool.md
+++ b/docs/command-line/promtool.md
@@ -181,7 +181,7 @@ Check if the rule files are valid or not.
 
 | Argument | Description |
 | --- | --- |
-| rule-files | The rule files to check, default is read from standard input (STDIN). |
+| rule-files | The rule files to check, default is read from standard input. |