diff --git a/pep-0484.txt b/pep-0484.txt
index 1f86e186c..70fa7cabd 100644
--- a/pep-0484.txt
+++ b/pep-0484.txt
@@ -217,8 +217,12 @@ alias::
     T = TypeVar('T', int, float, complex)
     Vector = Iterable[Tuple[T, T]]
 
-    def inproduct(v: Vector) -> T:
+    def inproduct(v: Vector[T]) -> T:
         return sum(x*y for x, y in v)
+    def dilate(v: Vector[T], scale: T) -> Vector[T]:
+        return ((x * scale, y * scale) for x, y in v)
+    vec = []  # type: Vector[float]
+
 
 This is equivalent to::
 
@@ -228,6 +232,9 @@ This is equivalent to::
 
     def inproduct(v: Iterable[Tuple[T, T]]) -> T:
         return sum(x*y for x, y in v)
+    def dilate(v: Iterable[Tuple[T, T]], scale: T) -> Iterable[Tuple[T, T]]:
+        return ((x * scale, y * scale) for x, y in v)
+    vec = []  # type: Iterable[Tuple[float, float]]
 
 
 Callable