diff --git a/SC2004.md b/SC2004.md
index 1ebfe7c..c5a7941 100644
--- a/SC2004.md
+++ b/SC2004.md
@@ -3,18 +3,18 @@
 ### Problematic code:
 
 ```sh
-echo $(($n+1))
+echo $(($n + ${arr[i]}))
 ```
 
 ### Correct code:
 
 ```sh
-echo $((n+1))
+echo $((n + arr[i]))
 ```
 
 ### Rationale:
 
-The `$` on regular variables in arithmetic contexts is unnecessary, and can even lead to subtle bugs. This is because the contents of `$((..))` is first expanded into a string, and then evaluated as an expression:
+The `$` or `${..}` on regular variables in arithmetic contexts is unnecessary, and can even lead to subtle bugs. This is because the contents of `$((..))` is first expanded into a string, and then evaluated as an expression:
 
 ```sh
 $ a='1+1'