diff --git a/docs/class.md b/docs/class.md
index f5dc1d8..78abb84 100644
--- a/docs/class.md
+++ b/docs/class.md
@@ -975,7 +975,7 @@ class Rectangle {
 
 class Square extends Rectangle {
   constructor(length) {
-    super(length, length);
+    super(length, width);
   }
 }