diff --git a/nix/ci.nix b/nix/ci.nix
index 183f8b3..4726fd9 100644
--- a/nix/ci.nix
+++ b/nix/ci.nix
@@ -1,6 +1,6 @@
 let
   sources = import ./sources.nix;
-  lib = import (sources."nixos-20.03" + "/lib");
+  lib = import (sources."nixos-unstable" + "/lib");
   inherit (import (sources."project.nix" + "/lib/dimension.nix") { inherit lib; }) dimension;
 in
 
@@ -14,16 +14,6 @@ dimension "Nixpkgs version" {
       enableDoc = false;
       nixosTestIsPerl = true;
     };
-    "nixos-19_09" = {
-      nixpkgsSource = "nixos-19.09";
-      enableDoc = false;
-      nixosTestIsPerl = true;
-    };
-    "nixos-20_03" = {
-      nixpkgsSource = "nixos-20.03";
-      isReferenceNixpkgs = false;
-      enableDoc = true;
-    };
     "nixos-20_09" = {
       nixpkgsSource = "nixos-20.09";
       isReferenceNixpkgs = true;
diff --git a/nix/sources.json b/nix/sources.json
index 067c7b0..47e0e6c 100644
--- a/nix/sources.json
+++ b/nix/sources.json
@@ -23,30 +23,6 @@
         "url": "https://github.com/NixOS/nixpkgs-channels/archive/34c7eb7545d155cc5b6f499b23a7cb1c96ab4d59.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     },
-    "nixos-19.09": {
-        "branch": "nixos-19.09",
-        "description": "A read-only mirror of NixOS/nixpkgs tracking the released channels. Send issues and PRs to",
-        "homepage": "https://github.com/NixOS/nixpkgs",
-        "owner": "NixOS",
-        "repo": "nixpkgs-channels",
-        "rev": "289466dd6a11c65a7de4a954d6ebf66c1ad07652",
-        "sha256": "0r5ja052s86fr54fm1zlhld3fwawz2w1d1gd6vbvpjrpjfyajibn",
-        "type": "tarball",
-        "url": "https://github.com/NixOS/nixpkgs-channels/archive/289466dd6a11c65a7de4a954d6ebf66c1ad07652.tar.gz",
-        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
-    },
-    "nixos-20.03": {
-        "branch": "release-20.03",
-        "description": "A read-only mirror of NixOS/nixpkgs tracking the released channels. Send issues and PRs to",
-        "homepage": "https://github.com/NixOS/nixpkgs",
-        "owner": "NixOS",
-        "repo": "nixpkgs",
-        "rev": "b4db68ff563895eea6aab4ff24fa04ef403dfe14",
-        "sha256": "1qbs7p0mmcmpg70ibd437hl57byqx5q0pc61p1dckrkazj7kq0pc",
-        "type": "tarball",
-        "url": "https://github.com/NixOS/nixpkgs/archive/b4db68ff563895eea6aab4ff24fa04ef403dfe14.tar.gz",
-        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
-    },
     "nixos-20.09": {
         "branch": "nixos-20.09",
         "description": "Nix Packages collection",