diff --git a/pkgs/python-packages.nix b/pkgs/python-packages.nix
--- a/pkgs/python-packages.nix
+++ b/pkgs/python-packages.nix
@@ -1589,13 +1589,13 @@
     };
   };
   pytz = super.buildPythonPackage {
-    name = "pytz-2018.3";
+    name = "pytz-2018.4";
     buildInputs = with self; [];
     doCheck = false;
     propagatedBuildInputs = with self; [];
     src = fetchurl {
-      url = "https://files.pythonhosted.org/packages/1b/50/4cdc62fc0753595fc16c8f722a89740f487c6e5670c644eb8983946777be/pytz-2018.3.tar.gz";
-      sha256 = "410bcd1d6409026fbaa65d9ed33bf6dd8b1e94a499e32168acfc7b332e4095c0";
+      url = "https://files.pythonhosted.org/packages/10/76/52efda4ef98e7544321fd8d5d512e11739c1df18b0649551aeccfb1c8376/pytz-2018.4.tar.gz";
+      sha256 = "c06425302f2cf668f1bba7a0a03f3c1d34d4ebeef2c72003da308b3947c7f749";
     };
     meta = {
       license = [ pkgs.lib.licenses.mit ];
diff --git a/requirements.txt b/requirements.txt
--- a/requirements.txt
+++ b/requirements.txt
@@ -61,7 +61,7 @@ python-dateutil
 python-ldap==2.4.45
 python-memcached==1.59
 python-pam==1.8.2
-pytz==2018.3
+pytz==2018.4
 tzlocal==1.5.1
 pyzmq==14.6.0
 py-gfm==0.1.3