diff --git a/develop/usage/configuration/homeserver_sample_config.html b/develop/usage/configuration/homeserver_sample_config.html

index f932eb2955..105760a28d 100644
--- a/develop/usage/configuration/homeserver_sample_config.html
+++ b/develop/usage/configuration/homeserver_sample_config.html
@@ -975,6 +975,12 @@ caches:
 # 'txn_limit' gives the maximum number of transactions to run per connection
 # before reconnecting. Defaults to 0, which means no limit.
 #
+# 'allow_unsafe_locale' is an option specific to Postgres. Under the default behavior, Synapse will refuse to
+# start if the postgres db is set to a non-C locale. You can override this behavior (which is *not* recommended)
+# by setting 'allow_unsafe_locale' to true. Note that doing so may corrupt your database. You can find more information
+# here: https://matrix-org.github.io/synapse/latest/postgres.html#fixing-incorrect-collate-or-ctype and here:
+# https://wiki.postgresql.org/wiki/Locale_data_changes
+#
 # 'args' gives options which are passed through to the database engine,
 # except for options starting 'cp_', which are used to configure the Twisted
 # connection pool. For a reference to valid arguments, see: