diff --git a/toolkit/components/telemetry/docs/environment.rst b/toolkit/components/telemetry/docs/environment.rst
index 449463947af0..f87bd34bf788 100644
--- a/toolkit/components/telemetry/docs/environment.rst
+++ b/toolkit/components/telemetry/docs/environment.rst
@@ -41,6 +41,7 @@ Structure::
           loadPath: <string>, // where the engine line is located; missing if no default
           submissionURL: <string> // missing if no default or for user-installed engines
         },
+        searchCohort: <string>, // optional, contains an identifier for any active search A/B experiments
         e10sEnabled: <bool>, // whether e10s is on, i.e. browser tabs open by default in a different process
         telemetryEnabled: <bool>, // false on failure
         isInOptoutSample: <bool>, // whether this client is part of the opt-out sample