diff --git a/.travis.yml b/.travis.yml
index 9f8bbce620..964c050c74 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -20,7 +20,7 @@ branches:
 install:
   - sudo curl -L https://nixos.org/nix/install | sh
   - . $HOME/.nix-profile/etc/profile.d/nix.sh
-  - nix-shell -I nixpgs=channel:nixos-unstable
+  - nix-shell
 
 script:
   - HYPOTHESIS_PROFILE=travis-ci pytest -v -k dataflow
diff --git a/shell.nix b/shell.nix
index 8e9ed1f19a..4425598c2a 100644
--- a/shell.nix
+++ b/shell.nix
@@ -1,13 +1,13 @@
-with import <nixpkgs> {};
+#with import <nixpkgs> {};
 
-# with import (builtins.fetchTarball {
-#   # Descriptive name to make the store path easier to identify
-#   name = "nixos-18.09";
-#   # Commit hash for nixos-unstable as of 2018-09-12
-#   url = "https://github.com/NixOS/nixpkgs/archive/18.09.tar.gz";
-#   # Hash obtained using `nix-prefetch-url --unpack <url>`
-#   sha256 = "1ib96has10v5nr6bzf7v8kw7yzww8zanxgw2qi1ll1sbv6kj6zpd";
-# }) {};
+with import (builtins.fetchTarball {
+  # Descriptive name to make the store path easier to identify
+  name = "nixos-19.09";
+  # Commit hash for nixos-unstable as of 2018-09-12
+  url = "https://github.com/NixOS/nixpkgs/archive/19.09.tar.gz";
+  # Hash obtained using `nix-prefetch-url --unpack <url>`
+  sha256 = "0mhqhq21y5vrr1f30qd2bvydv4bbbslvyzclhw0kdxmkgg3z4c92";
+}) {};
 
 let python = python37; in