diff --git a/uri.go b/uri.go
index 36e5373116..c663728f8c 100644
--- a/uri.go
+++ b/uri.go
@@ -33,9 +33,9 @@ type URI interface {
 	fmt.Stringer
 
 	// Extension should return the file extension of the resource
-	// referenced by the URI. For example, the Extension() of
-	// 'file://foo/bar.baz' is 'baz'. May return an empty string if the
-	// referenced resource has none.
+	// (including the dot) referenced by the URI. For example, the 
+	// Extension() of 'file://foo/bar.baz' is '.baz'. May return an
+	// empty string if the referenced resource has none.
 	Extension() string
 
 	// Name should return the base name of the item referenced by the URI.