diff --git a/support/doc/api/openapi.yaml b/support/doc/api/openapi.yaml
index 796c39119..160f363c5 100644
--- a/support/doc/api/openapi.yaml
+++ b/support/doc/api/openapi.yaml
@@ -8278,6 +8278,13 @@ components:
           description: >
             Event since last viewing call:
              * `seek` - If the user seeked the video
+        sessionId:
+          type: string
+          description: >
+            Optional param to represent the current viewer session.
+            Used by the backend to properly count one view per session per video.
+            PeerTube admin can configure the server to not trust this `sessionId` parameter but use the request IP address instead to identify a viewer.
+
 
     VideoStatsOverall:
       properties: