diff --git a/README.md b/README.md
index 0620890..a23a844 100644
--- a/README.md
+++ b/README.md
@@ -3,4 +3,6 @@
 ## Installation
 
 Edit `config.php` to your needs.  Afterwards, run `install.php`.  Make sure to
-delete this file after installation.
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+delete this file after installation.
+
+Don't forget to make the `tmp` directory writable for the webserver user.
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