diff --git a/postgres/content.md b/postgres/content.md
index 6212eb3e121e..54740d1b27fe 100644
--- a/postgres/content.md
+++ b/postgres/content.md
@@ -72,10 +72,12 @@ This optional environment variable can be used to define a different name for th
 
 This optional environment variable can be used to send arguments to `postgres initdb`. The value is a space separated string of arguments as `postgres initdb` would expect them. This is useful for adding functionality like data page checksums: `-e POSTGRES_INITDB_ARGS="--data-checksums"`.
 
-### `POSTGRES_INITDB_XLOGDIR`
+### `POSTGRES_INITDB_WALDIR`
 
 This optional environment variable can be used to define another location for the Postgres transaction log. By default the transaction log is stored in a subdirectory of the main Postgres data folder (`PGDATA`). Sometimes it can be desireable to store the transaction log in a different directory which may be backed by storage with different performance or reliability characteristics.
 
+**Note:** on PostgreSQL 9.x, this variable is `POSTGRES_INITDB_XLOGDIR` (reflecting [the changed name of the `--xlogdir` flag to `--waldir` in PostgreSQL 10+](https://wiki.postgresql.org/wiki/New_in_postgres_10#Renaming_of_.22xlog.22_to_.22wal.22_Globally_.28and_location.2Flsn.29)).
+
 ## Docker Secrets
 
 As an alternative to passing sensitive information via environment variables, `_FILE` may be appended to the previously listed environment variables, causing the initialization script to load the values for those variables from files present in the container. In particular, this can be used to load passwords from Docker secrets stored in `/run/secrets/<secret_name>` files. For example: