diff --git a/docs/compose-file.md b/docs/compose-file.md
index b55f250a8..682dacd3f 100644
--- a/docs/compose-file.md
+++ b/docs/compose-file.md
@@ -228,6 +228,8 @@ Custom DNS search domains. Can be a single value or a list.
 
 ### tmpfs
 
+> [Version 2 file format](#version-2) only.
+
 Mount a temporary file system inside the container. Can be a single value or a list.
 
     tmpfs: /run