diff --git a/nixos/modules/system/boot/tmp.nix b/nixos/modules/system/boot/tmp.nix
index 3775f17d763a..fd16cd3fba42 100644
--- a/nixos/modules/system/boot/tmp.nix
+++ b/nixos/modules/system/boot/tmp.nix
@@ -36,6 +36,11 @@ in
         default = false;
         description = lib.mdDoc ''
            Whether to mount a tmpfs on {file}`/tmp` during boot.
+
+           ::: {.note}
+           Large Nix builds can fail if the mounted tmpfs is not large enough.
+           In such a case either increase the tmpfsSize or disable this option.
+           :::
         '';
       };
     };