diff --git a/doc/manual/src/hacking.md b/doc/manual/src/hacking.md
index de8267206..ec96b8c69 100644
--- a/doc/manual/src/hacking.md
+++ b/doc/manual/src/hacking.md
@@ -15,12 +15,18 @@ and dependencies can be found:
 $ nix-shell
 ```
 
+of when flakes are enabled:
+
+```console
+$ nix develop
+```
+
 To build Hydra, you should then do:
 
 ```console
 [nix-shell]$ autoreconfPhase
 [nix-shell]$ configurePhase
-[nix-shell]$ make
+[nix-shell]$ make -j$(nproc)
 ```
 
 You start a local database, the webserver, and other components with