diff --git a/README.md b/README.md
index a7d61f4..77842cb 100644
--- a/README.md
+++ b/README.md
@@ -102,7 +102,7 @@ Set these in Gitea → Repository → Settings → Actions → Secrets:
 |--------|-------------|
 | `INVIDIOUS_DB_PASSWORD` | PostgreSQL password |
 | `INVIDIOUS_HMAC_KEY` | Generate: `openssl rand -hex 16` |
-| `INVIDIOUS_COMPANION_KEY` | Generate: `openssl rand -hex 16` (must match companion) |
+| `INVIDIOUS_COMPANION_KEY` | **Must be exactly 16 chars**: `openssl rand -base64 12` |
 
 ## Runner Setup