diff --git a/changelog.d/9801.doc b/changelog.d/9801.doc
new file mode 100644
index 000000000..8b8b9d01d
--- /dev/null
+++ b/changelog.d/9801.doc
@@ -0,0 +1 @@
+Add a note to the docker docs mentioning that we mirror upstream's supported Docker platforms.
diff --git a/docker/README.md b/docker/README.md
index 3a7dc585e..b65bcea63 100644
--- a/docker/README.md
+++ b/docker/README.md
@@ -2,9 +2,12 @@
 
 This Docker image will run Synapse as a single process. By default it uses a
 sqlite database; for production use you should connect it to a separate
-postgres database.
+postgres database. The image also does *not* provide a TURN server.
 
-The image also does *not* provide a TURN server.
+This image should work on all platforms that are supported by Docker upstream.
+Note that Docker's WS1-backend Linux Containers on Windows
+platform is [experimental](https://github.com/docker/for-win/issues/6470) and
+is not supported by this image.
 
 ## Volumes
 
@@ -208,4 +211,4 @@ healthcheck:
 ## Using jemalloc
 
 Jemalloc is embedded in the image and will be used instead of the default allocator.
-You can read about jemalloc by reading the Synapse [README](../README.md)
\ No newline at end of file
+You can read about jemalloc by reading the Synapse [README](../README.md)