diff --git a/docs/interpreter/shell.md b/docs/interpreter/shell.md
index b1efe38d0a..4db73d9031 100644
--- a/docs/interpreter/shell.md
+++ b/docs/interpreter/shell.md
@@ -71,7 +71,7 @@ please read [What is interpreter setting?](../usage/interpreter/overview.html#wh
 ## Kerberos refresh interval
 For changing the default behavior of when to renew Kerberos ticket following changes can be made in `conf/zeppelin-env.sh`.
 
-```
+```bash
 # Change Kerberos refresh interval (default value is 1d). Allowed postfix are ms, s, m, min, h, and d.
 export LAUNCH_KERBEROS_REFRESH_INTERVAL=4h
 # Change kinit number retries (default value is 5), which means if the kinit command fails for 5 retries consecutively it will close the interpreter.