diff --git a/docs/references/selfhosting.md b/docs/references/selfhosting.md
index 7c0b5ac5d..27bda70c5 100644
--- a/docs/references/selfhosting.md
+++ b/docs/references/selfhosting.md
@@ -95,7 +95,8 @@ Initially a self-signed one is provided, which can be overwritten later in the a
 This may be useful for non-public installations.
 
 
-* `--data-dir` is the path where Cloudron will store platform and application data.
+* `--data-dir` is the path where Cloudron will store platform and application data. Note: data
+directory must be an `ext4` filesystem.
 
 Optional arguments used for update and restore:
 
@@ -471,6 +472,8 @@ The goal of rate limits is to prevent password brute force attacks.
 If you are installing a brand new Cloudron, you can configure the data directory
 that Cloudron uses by passing the `--data-dir` option to `cloudron-setup`.
 
+Note: data directory must be an `ext4` filesystem.
+
 ```
 ./cloudron-setup --provider <digitalocean|ec2|generic|scaleway> --data-dir /var/cloudrondata
 ```