diff --git a/config.md b/config.md
index d4b593f25..d9e065b0b 100644
--- a/config.md
+++ b/config.md
@@ -149,7 +149,8 @@ Note: Any OPTIONAL field MAY also be set to null, which is equivalent to being a
    - **Volumes** *object*, OPTIONAL
 
      A set of directories which SHOULD be created as data volumes in a container running this image.
-     If a file or folder exists within the image with the same path as a data volume, that file or folder will be replaced by the data volume and never be merged.
+     If a file or folder exists within the image with the same path as a data volume, that file or folder MUST be replaced by the data volume and never be merged.
+     When a new layer is created from a container that has data volumes, any data within the data volume SHOULD NOT be included in the changeset layer.
      **NOTE:** This JSON structure value is unusual because it is a direct JSON serialization of the Go type `map[string]struct{}` and is represented in JSON as an object mapping its keys to an empty object.
 
    - **WorkingDir** *string*, OPTIONAL