diff --git a/ci/eval/outpaths.nix b/ci/eval/outpaths.nix
index 512290ce450a8..b8377b5e91bc9 100755
--- a/ci/eval/outpaths.nix
+++ b/ci/eval/outpaths.nix
@@ -83,8 +83,6 @@ let
             inHydra = true;
           }
           // extraNixpkgsConfig;
-
-          __allowFileset = false;
         };
       };
 
diff --git a/pkgs/top-level/default.nix b/pkgs/top-level/default.nix
index c9e888067a741..ec9511cfc4a92 100644
--- a/pkgs/top-level/default.nix
+++ b/pkgs/top-level/default.nix
@@ -30,11 +30,11 @@ let
   # there’s nothing we can do about that within the constraints of the
   # Nix language.
   x86_64DarwinDeprecationWarning =
-    pristineLib.warn
+    lib.warn
       "Nixpkgs 26.05 will be the last release to support x86_64-darwin; see https://nixos.org/manual/nixpkgs/unstable/release-notes#x86_64-darwin-26.05"
       (x: x);
 
-  pristineLib = import ../../lib;
+  lib = import ../../lib;
 in
 
 {
@@ -49,10 +49,6 @@ in
   # Allow a configuration attribute set to be passed in as an argument.
   config ? { },
 
-  # Temporary hack to let Nixpkgs forbid internal use of `lib.fileset`
-  # until <https://github.com/NixOS/nix/issues/11503> is fixed.
-  __allowFileset ? true,
-
   # List of overlays layers used to extend Nixpkgs.
   overlays ? [ ],
 
@@ -68,31 +64,16 @@ in
   ...
 }@args:
 
+assert
+  args ? __allowFileset
+  -> throw "__allowFileset option was removed as it's no longer neeed, please remove it.";
+
 let # Rename the function arguments
   config0 = config;
   crossSystem0 = crossSystem;
 
 in
 let
-  lib =
-    if __allowFileset then
-      pristineLib
-    else
-      pristineLib.extend (
-        _: _: {
-          fileset = abort ''
-
-            The use of `lib.fileset` is currently forbidden in Nixpkgs due to the
-            upstream Nix bug <https://github.com/NixOS/nix/issues/11503>. This
-            causes difficult‐to‐debug errors when combined with chroot stores,
-            such as in the NixOS installer.
-
-            For packages that require source to be vendored inside Nixpkgs,
-            please use a subdirectory of the package instead.
-          '';
-        }
-      );
-
   inherit (lib) throwIfNot;
 
   checked =
diff --git a/pkgs/top-level/release-cross.nix b/pkgs/top-level/release-cross.nix
index 13fda84028ddc..1799f86529fe2 100644
--- a/pkgs/top-level/release-cross.nix
+++ b/pkgs/top-level/release-cross.nix
@@ -29,7 +29,6 @@
       allowUnfree = false;
       inHydra = true;
     };
-    __allowFileset = false;
   },
 }:
 
diff --git a/pkgs/top-level/release-cuda.nix b/pkgs/top-level/release-cuda.nix
index b7111fedb63e1..05a0b2e97b5b3 100644
--- a/pkgs/top-level/release-cuda.nix
+++ b/pkgs/top-level/release-cuda.nix
@@ -34,8 +34,6 @@ in
       # Don't evaluate duplicate and/or deprecated attributes
       allowAliases = false;
     };
-
-    __allowFileset = false;
   },
   ...
 }@args:
diff --git a/pkgs/top-level/release-lib.nix b/pkgs/top-level/release-lib.nix
index 6bbcc48ee6514..6d1e9dc37daaa 100644
--- a/pkgs/top-level/release-lib.nix
+++ b/pkgs/top-level/release-lib.nix
@@ -10,7 +10,6 @@
       allowUnfree = false;
       inHydra = true;
     };
-    __allowFileset = false;
   },
 }:
 
diff --git a/pkgs/top-level/release-python.nix b/pkgs/top-level/release-python.nix
index 47b2133368b3e..d552651eaad37 100644
--- a/pkgs/top-level/release-python.nix
+++ b/pkgs/top-level/release-python.nix
@@ -16,8 +16,6 @@
       allowUnfree = false;
       inHydra = true;
     };
-
-    __allowFileset = false;
   },
 }:
 
diff --git a/pkgs/top-level/release-staging.nix b/pkgs/top-level/release-staging.nix
index a789bb29e0155..1a106513b974f 100644
--- a/pkgs/top-level/release-staging.nix
+++ b/pkgs/top-level/release-staging.nix
@@ -19,7 +19,6 @@
       allowUnfree = false;
       inHydra = true;
     };
-    __allowFileset = false;
   },
 }:
 
diff --git a/pkgs/top-level/release-unfree-redistributable.nix b/pkgs/top-level/release-unfree-redistributable.nix
index cf5c8a4d4987e..b3e7dad404399 100644
--- a/pkgs/top-level/release-unfree-redistributable.nix
+++ b/pkgs/top-level/release-unfree-redistributable.nix
@@ -37,8 +37,6 @@
       cudaSupport = true;
       inHydra = true;
     };
-
-    __allowFileset = false;
   },
   # We only build the full package set on infrequently releasing channels.
   full ? false,
diff --git a/pkgs/top-level/release.nix b/pkgs/top-level/release.nix
index c8b59f37e0aef..87833f9e5658c 100644
--- a/pkgs/top-level/release.nix
+++ b/pkgs/top-level/release.nix
@@ -49,8 +49,6 @@
         "kanidmWithSecretProvisioning_1_8-1.8.6"
       ];
     };
-
-    __allowFileset = false;
   },
 
   # This flag, if set to true, will inhibit the use of `mapTestOn`