diff --git a/src/oas.md b/src/oas.md
index a0e4cb8899..d5b3645174 100644
--- a/src/oas.md
+++ b/src/oas.md
@@ -1963,6 +1963,7 @@ requestBody:
   content:
     multipart/form-data:
       schema:
+        type: object
         properties:
           # The property name `file` will be used for all files.
           file: