diff --git a/docs/config.md b/docs/config.md
index 1903c70efd..d9a7ca3963 100644
--- a/docs/config.md
+++ b/docs/config.md
@@ -550,3 +550,4 @@ The following are undocumented or intended for developer use only.
 2. `sync_timeline_limit`
 3. `dangerously_allow_unsafe_and_insecure_passwords`
 4. `latex_maths_delims`: An optional setting to override the default delimiters used for maths parsing. See https://github.com/matrix-org/matrix-react-sdk/pull/5939 for details. Only used when `feature_latex_maths` is enabled.
+5. `voice_broadcast.chunk_length`: Target chunk length in seconds for the Voice Broadcast feature currently under development.