diff --git a/api/client-server/v2_alpha/definitions/event_filter.json b/api/client-server/v2_alpha/definitions/event_filter.json
index c15b8133..269bb5f0 100644
--- a/api/client-server/v2_alpha/definitions/event_filter.json
+++ b/api/client-server/v2_alpha/definitions/event_filter.json
@@ -17,7 +17,7 @@
     "not_types": {
       "type": "array",
       "description":
-        "A list of event types to exclude. If this list is absent then no event types are excluded.",
+        "A list of event types to exclude. If this list is absent then no event types are excluded. A matching type will be excluded even if it is listed in the 'types' filter",
       "items": {
         "type": "string"
       }
@@ -33,7 +33,7 @@
     "not_senders": {
       "type": "array",
       "description":
-        "A list of sender IDs to exclude. If this list is absent then no senders are excluded.",
+        "A list of sender IDs to exclude. If this list is absent then no senders are excluded. A matching sender will be excluded even if it is listed in the 'senders' filter",
       "items": {
         "type": "string"
       }
diff --git a/api/client-server/v2_alpha/definitions/room_event_filter.json b/api/client-server/v2_alpha/definitions/room_event_filter.json
index c234448e..5be0fcd2 100644
--- a/api/client-server/v2_alpha/definitions/room_event_filter.json
+++ b/api/client-server/v2_alpha/definitions/room_event_filter.json
@@ -1,5 +1,6 @@
 {
   "type": "object",
+  "allOf": [{"$ref": "definitions/event_filter.json"}],
   "properties": {
     "rooms": {
       "type": "array",
@@ -12,7 +13,7 @@
     "not_rooms": {
       "type": "array",
       "description":
-        "A list of room IDs to exclude. If this list is absent then no rooms are excluded.",
+        "A list of room IDs to exclude. If this list is absent then no rooms are excluded. A matching room will be excluded even if it is listed in the 'rooms' filter",
       "items": {
         "type": "string"
       }