Fix wrong sub chapter for external checks

diff --git a/doc/08-advanced-topics.md b/doc/08-advanced-topics.md
index 25e66034f560d9476982d9dd034711099da69e14..00d1b075a9b74793c32d1be2c04e22f89ebca878 100644 (file)
--- a/doc/08-advanced-topics.md
+++ b/doc/08-advanced-topics.md
@@ -343,7 +343,7 @@ and adds the excluded time period names as an array.
       }
     }
 
-### External Check Results <a id="external-check-results"></a>
+## External Check Results <a id="external-check-results"></a>
 
 Hosts or services which do not actively execute a check plugin to receive
 the state and output are called "passive checks" or "external check results".