diff --git a/docs/20_Checks/check_ceph_diskfree.md b/docs/20_Checks/check_ceph_diskfree.md
index 3686600f11576603cce74698c5172cb7b39232c9..e1425b6748a3bbacb72aaeba14f567cea88d85ba 100644
--- a/docs/20_Checks/check_ceph_diskfree.md
+++ b/docs/20_Checks/check_ceph_diskfree.md
@@ -15,7 +15,7 @@ icingaclient ALL=(ALL) NOPASSWD: /bin/ceph
 
 ## Syntax
 
-```
+```txt
 $ check_ceph_diskfree -h
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