diff --git a/default.nix b/default.nix
index c5f49a372..21a17bdef 100644
--- a/default.nix
+++ b/default.nix
@@ -1,8 +1,7 @@
 let
   # sources.nix contains information about which versions of some of our
-  # dependencies we should use.  since we use it to pin nixpkgs and the PyPI
-  # package database, roughly all the rest of our dependencies are *also*
-  # pinned - indirectly.
+  # dependencies we should use.  since we use it to pin nixpkgs, all the rest
+  # of our dependencies are *also* pinned - indirectly.
   #
   # sources.nix is managed using a tool called `niv`.  as an example, to
   # update to the most recent version of nixpkgs from the 21.11 maintenance
@@ -10,11 +9,6 @@ let
   #
   #   niv update nixpkgs-21.11
   #
-  # or, to update the PyPI package database -- which is necessary to make any
-  # newly released packages visible -- you likewise run:
-  #
-  #   niv update pypi-deps-db
-  #
   # niv also supports chosing a specific revision, following a different
   # branch, etc.  find complete documentation for the tool at
   # https://github.com/nmattia/niv