diff --git a/snippets/countBy.md b/snippets/countBy.md
index 16aacca5e..f3b7acfb4 100644
--- a/snippets/countBy.md
+++ b/snippets/countBy.md
@@ -7,7 +7,7 @@ Use `Array.prototype.reduce()` to create an object, where the keys are produced
 
 ```js
 const countBy = (arr, fn) =>
-  arr.map(typeof fn === 'function' ? fn : val => val[fn]).reduce((acc, val, i) => {
+  arr.map(typeof fn === 'function' ? fn : val => val[fn]).reduce((acc, val) => {
     acc[val] = (acc[val] || 0) + 1;
     return acc;
   }, {});
diff --git a/test/countBy/countBy.js b/test/countBy/countBy.js
index e6b0cadf6..83f16c1b7 100644
--- a/test/countBy/countBy.js
+++ b/test/countBy/countBy.js
@@ -1,5 +1,5 @@
 const countBy = (arr, fn) =>
-  arr.map(typeof fn === 'function' ? fn : val => val[fn]).reduce((acc, val, i) => {
+  arr.map(typeof fn === 'function' ? fn : val => val[fn]).reduce((acc, val) => {
     acc[val] = (acc[val] || 0) + 1;
     return acc;
   }, {});