diff --git a/docs/book/20-Generics.md b/docs/book/20-Generics.md
index b03c5e64..6b0c0517 100644
--- a/docs/book/20-Generics.md
+++ b/docs/book/20-Generics.md
@@ -1409,7 +1409,7 @@ class Manipulator3 {
     private HasF obj;
     
     Manipulator3(HasF x) {
-        ojb = x;
+        obj = x;
     }
     
     public void manipulate() {