diff --git a/guides/source/action_view_overview.md b/guides/source/action_view_overview.md
index 6c2871d478..4cdac43a7e 100644
--- a/guides/source/action_view_overview.md
+++ b/guides/source/action_view_overview.md
@@ -1264,7 +1264,7 @@ Creates a field set for grouping HTML form elements.
 Creates a file upload field.
 
 ```html+erb
-<%= form_tag {action: "post"} do %>
+<%= form_tag {action: "post"}, {multipart: true} do %>
   <label for="file">File to Upload</label> <%= file_field_tag "file" %>
   <%= submit_tag %>
 <% end %>