diff --git a/.circleci/config.yml b/.circleci/config.yml
index 96e8e38fc1fba9df1355fb5d5446a11e640456c3..9cd2b20cbaae07e50e7cea351c05ed72183d46b4 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -60,7 +60,7 @@ jobs:
       # time of this comment.  We can bump it to a newer version when that
       # makes sense.  Meanwhile, the platform won't shift around beneath us
       # unexpectedly.
-      NIXPKGS_REV: "5d5cd70516001e79516d2ade8bcf31df208a4ef3"
+      NIXPKGS_REV: "8bf142e001b6876b021c8ee90c2c7cec385fe8e9"
 
     steps:
       - run:
diff --git a/autobahn.nix b/autobahn.nix
deleted file mode 100644
index df026096799d6b65bf34ad7700b6a726e9252f68..0000000000000000000000000000000000000000
--- a/autobahn.nix
+++ /dev/null
@@ -1,38 +0,0 @@
-{ lib, buildPythonPackage, fetchFromGitHub, isPy3k,
-  six, txaio, twisted, zope_interface, cffi, trollius, futures, cryptography,
-  mock, pytest,
-  supportAsyncio ? false
-}:
-buildPythonPackage rec {
-  pname = "autobahn";
-  version = "19.7.1";
-
-  src = fetchFromGitHub {
-    owner = "crossbario";
-    repo = "autobahn-python";
-    rev = "v${version}";
-    sha256 = "1gl2m18s77hlpiglh44plv3k6b965n66ylnxbzgvzcdl9jf3l3q3";
-  };
-
-  propagatedBuildInputs = [ six txaio twisted zope_interface cffi cryptography ] ++
-    (lib.optionals (!isPy3k) [ futures ]) ++
-    (lib.optionals (supportAsyncio && !isPy3k) [ trollius ])
-    ;
-
-  checkInputs = [ mock pytest ];
-  checkPhase = ''
-    runHook preCheck
-    USE_TWISTED=true py.test $out
-    runHook postCheck
-  '';
-
-  # XXX Fails for some reason I don't understand.
-  doCheck = false;
-
-  meta = with lib; {
-    description = "WebSocket and WAMP in Python for Twisted and asyncio.";
-    homepage    = "https://crossbar.io/autobahn";
-    license     = licenses.mit;
-    maintainers = with maintainers; [ nand0p ];
-  };
-}
diff --git a/cryptography.nix b/cryptography.nix
deleted file mode 100644
index bfa6d30208387b334af63b072b3e409b6d39a063..0000000000000000000000000000000000000000
--- a/cryptography.nix
+++ /dev/null
@@ -1,75 +0,0 @@
-{ stdenv
-, buildPythonPackage
-, fetchFromGitHub
-, openssl
-, cryptography_vectors
-, darwin
-, asn1crypto
-, packaging
-, six
-, pythonOlder
-, enum34
-, ipaddress
-, isPyPy
-, cffi
-, pytest
-, pretend
-, iso8601
-, pytz
-, hypothesis
-}:
-
-buildPythonPackage rec {
-  pname = "cryptography";
-  version = "2.7"; # Also update the hash in vectors.nix
-
-  src = fetchFromGitHub {
-    owner = "pyca";
-    repo = "cryptography";
-    rev = "2.7";
-    sha256 = "145byri5c3b8m6dbhwb6yxrv9jrr652l3z1w16mz205z8dz38qja";
-  };
-
-  outputs = [ "out" "dev" ];
-
-  buildInputs = [ openssl ]
-             ++ stdenv.lib.optional stdenv.isDarwin darwin.apple_sdk.frameworks.Security;
-  propagatedBuildInputs = [
-    asn1crypto
-    packaging
-    six
-  ] ++ stdenv.lib.optional (pythonOlder "3.4") enum34
-  ++ stdenv.lib.optional (pythonOlder "3.3") ipaddress
-  ++ stdenv.lib.optional (!isPyPy) cffi;
-
-  checkInputs = [
-    cryptography_vectors
-    hypothesis
-    iso8601
-    pretend
-    pytest
-    pytz
-  ];
-
-  checkPhase = ''
-    py.test --disable-pytest-warnings tests
-  '';
-
-  # IOKit's dependencies are inconsistent between OSX versions, so this is the best we
-  # can do until nix 1.11's release
-  __impureHostDeps = [ "/usr/lib" ];
-
-  meta = with stdenv.lib; {
-    description = "A package which provides cryptographic recipes and primitives";
-    longDescription = ''
-      Cryptography includes both high level recipes and low level interfaces to
-      common cryptographic algorithms such as symmetric ciphers, message
-      digests, and key derivation functions.
-      Our goal is for it to be your "cryptographic standard library". It
-      supports Python 2.7, Python 3.4+, and PyPy 5.3+.
-    '';
-    homepage = https://github.com/pyca/cryptography;
-    license = with licenses; [ asl20 bsd3 psfl ];
-    maintainers = with maintainers; [ primeos ];
-  };
-}
diff --git a/cryptography_vectors.nix b/cryptography_vectors.nix
deleted file mode 100644
index ea24ed908016b8ad2a534923709072b171b00b9a..0000000000000000000000000000000000000000
--- a/cryptography_vectors.nix
+++ /dev/null
@@ -1,23 +0,0 @@
-{ buildPythonPackage, fetchPypi, lib, cryptography }:
-
-buildPythonPackage rec {
-  pname = "cryptography_vectors";
-  # The test vectors must have the same version as the cryptography package:
-  version = cryptography.version;
-
-  src = fetchPypi {
-    inherit pname version;
-    sha256 = "1g38zw90510azyfrj6mxbslx2gp9yrnv5dac0w2819k9ssdznbgi";
-  };
-
-  # No tests included
-  doCheck = false;
-
-  meta = with lib; {
-    description = "Test vectors for the cryptography package";
-    homepage = https://cryptography.io/en/latest/development/test-vectors/;
-    # Source: https://github.com/pyca/cryptography/tree/master/vectors;
-    license = with licenses; [ asl20 bsd3 ];
-    maintainers = with maintainers; [ primeos ];
-  };
-}
diff --git a/overlays.nix b/overlays.nix
index 1d4048e5031af8e8c8d785c662bfb8750bbcbf0f..06a2aab9df437cd1b7b32ad3c5e87c848ac7c17c 100644
--- a/overlays.nix
+++ b/overlays.nix
@@ -13,28 +13,21 @@ self: super: {
       # ecosystem - the early stages of a slow, painful death by the thousand
       # cuts of incompatibilities between libraries with no maintained Python
       # 2 support.
-      typing = python-super.callPackage ./typing.nix { };
+      typing = python-self.callPackage ./typing.nix { };
 
       # new tahoe-lafs dependency
-      eliot = python-super.callPackage ./eliot.nix { };
-      # new autobahn requires a newer cryptography
-      cryptography = python-super.callPackage ./cryptography.nix { };
-      # new cryptography requires a newer cryptography_vectors
-      cryptography_vectors = python-super.callPackage ./cryptography_vectors.nix { };
-      # new tahoe-lafs depends on a very recent autobahn for better
-      # websocket testing features.
-      autobahn = python-super.callPackage ./autobahn.nix { };
+      eliot = python-self.callPackage ./eliot.nix { };
 
       # tahoe-lafs in nixpkgs is packaged as an application!  so we have to
       # re-package it ourselves as a library.
-      tahoe-lafs = python-super.callPackage ./tahoe-lafs.nix { };
+      tahoe-lafs = python-self.callPackage ./tahoe-lafs.nix { };
 
       # we depend on the privacypass python library, a set of bindings to the
       # challenge-bypass-ristretto Rust library
-      privacypass = python-super.callPackage ./privacypass.nix { };
+      privacypass = python-self.callPackage ./privacypass.nix { };
 
       # And add ourselves to the collection too.
-      zkapauthorizer = python-super.callPackage ./zkapauthorizer.nix { };
+      zkapauthorizer = python-self.callPackage ./zkapauthorizer.nix { };
     };
   };
 }