diff --git a/doc/manual/hacking.xml b/doc/manual/hacking.xml
index d25d4b84a..5d9f08d38 100644
--- a/doc/manual/hacking.xml
+++ b/doc/manual/hacking.xml
@@ -32,7 +32,7 @@ i686-linux, x86_64-darwin, x86_64-linux.
 i.e.
 
 <screen>
-nix-build -A defaultPackage.x86_64-linux
+$ nix-build -A defaultPackage.x86_64-linux
 </screen>
 
 </para>