diff --git a/mix.exs b/mix.exs
index 4bc0f34..8162e60 100644
--- a/mix.exs
+++ b/mix.exs
@@ -53,7 +53,7 @@ defmodule ExCell.Mixfile do
       {:mix_test_watch, "~> 0.3", only: :dev, runtime: false},
       {:phoenix_html, "~> 2.10"},
       {:phoenix, "~> 1.4.0", optional: true},
-      {:poison, "~> 3.1"},
+      {:poison, "~> 4.0"},
       {:uuid, "~> 1.1"}
     ]
   end
diff --git a/mix.lock b/mix.lock
index 301dd75..24af012 100644
--- a/mix.lock
+++ b/mix.lock
@@ -27,7 +27,7 @@
   "phoenix_pubsub": {:hex, :phoenix_pubsub, "1.1.1", "6668d787e602981f24f17a5fbb69cc98f8ab085114ebfac6cc36e10a90c8e93c", [:mix], [], "hexpm"},
   "plug": {:hex, :plug, "1.7.1", "8516d565fb84a6a8b2ca722e74e2cd25ca0fc9d64f364ec9dbec09d33eb78ccd", [:mix], [{:mime, "~> 1.0", [hex: :mime, repo: "hexpm", optional: false]}, {:plug_crypto, "~> 1.0", [hex: :plug_crypto, repo: "hexpm", optional: false]}], "hexpm"},
   "plug_crypto": {:hex, :plug_crypto, "1.0.0", "18e49317d3fa343f24620ed22795ec29d4a5e602d52d1513ccea0b07d8ea7d4d", [:mix], [], "hexpm"},
-  "poison": {:hex, :poison, "3.1.0", "d9eb636610e096f86f25d9a46f35a9facac35609a7591b3be3326e99a0484665", [:mix], [], "hexpm"},
+  "poison": {:hex, :poison, "4.0.1", "bcb755a16fac91cad79bfe9fc3585bb07b9331e50cfe3420a24bcc2d735709ae", [:mix], [], "hexpm"},
   "ssl_verify_fun": {:hex, :ssl_verify_fun, "1.1.4", "f0eafff810d2041e93f915ef59899c923f4568f4585904d010387ed74988e77b", [:make, :mix, :rebar3], [], "hexpm"},
   "unicode_util_compat": {:hex, :unicode_util_compat, "0.4.1", "d869e4c68901dd9531385bb0c8c40444ebf624e60b6962d95952775cac5e90cd", [:rebar3], [], "hexpm"},
   "uuid": {:hex, :uuid, "1.1.8", "e22fc04499de0de3ed1116b770c7737779f226ceefa0badb3592e64d5cfb4eb9", [], [], "hexpm"},