diff --git a/exercises/implement_map_with_reduce/problem.md b/exercises/implement_map_with_reduce/problem.md
index 015030d..807c653 100644
--- a/exercises/implement_map_with_reduce/problem.md
+++ b/exercises/implement_map_with_reduce/problem.md
@@ -37,7 +37,7 @@ console.log(output) // => [2,4,6,8,10]
 
 ```js
 
-function arrayMap(arr, fn) {
+function arrayMap(arr, fn, thisArg) {
   //SOLUTION GOES HERE
 }