diff --git a/schemas/README-EDDN-schemas.md b/schemas/README-EDDN-schemas.md
index a245d11..37ac5b3 100644
--- a/schemas/README-EDDN-schemas.md
+++ b/schemas/README-EDDN-schemas.md
@@ -248,10 +248,13 @@ Each `message` object must have, at bare minimum:
    will be much more than this. Consult the
    [schemas and their documentation](./).
 3. Where the data is sourced from a Journal event please do preserve the
-   event key and value.  Yes, where we use an event-specific schema this
+   `event` key and value.  Yes, where we use an event-specific schema this
    might seem redundant, but it might aid an EDDN listener in streamlining
    their code, and it does no harm.
 
+   Any new schema based on Journal data **MUST** make `event` a required
+   property of the `message` dictionary.
+
 Because the first versions of some schemas were defined when only the CAPI 
 data was available, before Journal files existed, many of the key names chosen
 in the schemas are based on the equivalent in CAPI data, not Journal events.