1 files changed, 2 insertions, 1 deletions
diff --git a/docker/README.md b/docker/README.md
index eda3221c23..08372e95c6 100644
--- a/docker/README.md
+++ b/docker/README.md
@@ -73,7 +73,8 @@ The following environment variables are supported in `generate` mode:
   will log sensitive information such as access tokens.
   This should not be needed unless you are a developer attempting to debug something
   particularly tricky.
-
+* `SYNAPSE_LOG_TESTING`: if set, Synapse will log additional information useful
+  for testing.
 
 ## Postgres