diff --git a/README.md b/README.md
index f6e7a77..d07297a 100644
--- a/README.md
+++ b/README.md
@@ -9,7 +9,10 @@ solution like [PathVector][pv].
 ## Quick start
 
 1. Make sure `bird` 2.x is installed, e.g. on Debian or Ubuntu, through
-   `sudo apt install bird2`.
+   `sudo apt install bird2`. This library has not been tested on versions
+   older than 2.0.13, so you may run into syntax errors on earlier versions.
+   In these cases, you'll need to look into backports or PPAs for a newer
+   version.
 2. Clone this repository:
    ```
    git clone https://github.com/quantum5/bird-filter.git