diff --git a/README.md b/README.md
index 67fd258..f95d995 100644
--- a/README.md
+++ b/README.md
@@ -6,6 +6,16 @@ Generate graphs from an IMAP mailbox.
 
 I use this repo to play around with Nix flakes.
 
+### Required configuration
+
+In `~/.config/nix/nix.conf`:
+
+```
+experimental-features = nix-command flakes
+```
+
+This enables `nix *` commands and flakes.
+
 ### Run on M1
 
 The Python OpenSSL package is currently broken on M1. To run Jupyter Lab using Rosetta emulation: