diff --git a/pkgs/top-level/python-packages.nix b/pkgs/top-level/python-packages.nix
index 1ca0a76d6bb..15c1b2bbb28 100644
--- a/pkgs/top-level/python-packages.nix
+++ b/pkgs/top-level/python-packages.nix
@@ -431,15 +431,19 @@ in {
   };
 
   altair = buildPythonPackage rec {
-    name = "altair-1.0.0";
+    name = "altair-1.2.0";
 
     src = pkgs.fetchurl {
       url = "mirror://pypi/a/altair/${name}.tar.gz";
-      sha256 = "024drhmiw8w3dl7dbal0pvnlfd3sv4n1rqywv2jb488b3fzm704r";
+      sha256 = "05c47dm20p7m0017p2h38il721rxag1q0457dj7whp0k8rc7qd1n";
     };
+    buildInputs = [ self.pytest ];
 
+    checkPhase = ''
+      export LANG=en_US.UTF-8
+      py.test altair --doctest-modules
+    '';
     propagatedBuildInputs = with self; [ vega pandas ipython traitlets ];
-
     meta = {
       description = "A declarative statistical visualization library for Python.";
       homepage = https://github.com/altair-viz/altair;