diff --git a/dev-docs/bidders/tappx.md b/dev-docs/bidders/tappx.md
index 46673da937..0797111f67 100644
--- a/dev-docs/bidders/tappx.md
+++ b/dev-docs/bidders/tappx.md
@@ -23,9 +23,9 @@ Please contact tappx@tappx.com to get set up.
 {: .table .table-bordered .table-striped }
 | Name       | Scope    | Description            | Example | Type     |
 |------------|----------|------------------------|---------|----------|
-| host | required | Tappx host | 'host1' | string |
 | tappxkey | required | An ID which identifies the adunit | 'key1' | string |
 | endpoint | required | Endpoint provided to publisher | 'endpoint1' | string |
+| host | required(pbjs) optional(pbserver) | Tappx host | 'host1' | string |
 | bidfloor | optional | Minimum bid for this impression expressed in CPM (USD) | 1.2 | number |
 | mktag | optional | An ID which identifies a group of adunits | 'key1' | string |
 | bcid | optional | Block list of CID | ["1234"] | array of strings |
@@ -34,3 +34,6 @@ Please contact tappx@tappx.com to get set up.
 ### Test Parameters
 
 Use the official test parameter specified in the oRTB standard (https://github.com/InteractiveAdvertisingBureau/openrtb/blob/master/OpenRTB%20v3.0%20FINAL.md#object_request)
+
+### Other notes
+- Parameters host is required in prebidjs and the old versions of prebid server. In case of doubt, always add the parameter.