diff --git a/doc/manual/src/hacking.md b/doc/manual/src/hacking.md
index 1f1761a7..ec96b8c6 100644
--- a/doc/manual/src/hacking.md
+++ b/doc/manual/src/hacking.md
@@ -26,7 +26,7 @@ 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