1 files changed, 15 insertions, 0 deletions
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 864c644ca885a..07723d5804130 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -24,6 +24,21 @@ let
 
 in
 {
+  # A module system style type tag
+  #
+  # Allows the nixpkgs fixpoint, usually known as `pkgs`
+  # to be distinguished nominally.
+  #
+  #     pkgs._type == "pkgs"
+  #     pkgs.pkgsStatic._type == "pkgs"
+  #
+  # Design note:
+  # While earlier stages of nixpkgs fixpoint construction
+  # are supertypes of this stage, they're generally not
+  # usable in places where a `pkgs` is expected.
+  # (earlier stages being the various `super` variables
+  #  that precede all-packages.nix)
+  _type = "pkgs";
 
   # Allow callPackage to fill in the pkgs argument
   inherit pkgs;