diff --git a/exercises/exercise-4.md b/exercises/exercise-4.md
index 018df7d4dc393ffa7f6848f30be6f060463cd696..f82f15c9552749e2667ae513a99f01564deeb6f5 100644
--- a/exercises/exercise-4.md
+++ b/exercises/exercise-4.md
@@ -13,8 +13,6 @@ First of all, spend some time as a group to make sure that you understand what t
 ```scala
 extension [T](self: MyFuture[T])
   def map[S](f: T => S): MyFuture[S] = ???
-
-extension [T](self: MyFuture[T])
   def filter(p: T => Boolean): MyFuture[T] = ???
 ```
 
diff --git a/exercises/exercise-4.pdf b/exercises/exercise-4.pdf
new file mode 100644
index 0000000000000000000000000000000000000000..04977b3ad554cab8b79183d65e504a9e2b3cafff
Binary files /dev/null and b/exercises/exercise-4.pdf differ