diff --git a/doc/manual/command-ref/nix-collect-garbage.xml b/doc/manual/command-ref/nix-collect-garbage.xml
index c8885129..35a78c5b 100644
--- a/doc/manual/command-ref/nix-collect-garbage.xml
+++ b/doc/manual/command-ref/nix-collect-garbage.xml
@@ -28,6 +28,7 @@
+ bytes