diff --git a/mix.exs b/mix.exs
index 227b087..bf3fd74 100644
--- a/mix.exs
+++ b/mix.exs
@@ -14,7 +14,8 @@ defmodule X509.MixProject do
       description: description(),
       package: package(),
       docs: docs(),
-      source_url: "https://github.com/voltone/x509"
+      source_url: "https://github.com/voltone/x509",
+      dialyzer: [plt_add_apps: [:mix, :syntax_tools]]
     ]
   end
 
@@ -28,7 +29,8 @@ defmodule X509.MixProject do
   # Run "mix help deps" to learn about dependencies.
   defp deps do
     [
-      {:ex_doc, "~> 0.19", only: :dev}
+      {:ex_doc, "~> 0.19", only: :dev},
+      {:dialyxir, "1.0.0-rc.4", only: :dev, runtime: false}
     ]
   end
 
diff --git a/mix.lock b/mix.lock
index 8ff453d..3372e64 100644
--- a/mix.lock
+++ b/mix.lock
@@ -1,5 +1,7 @@
 %{
+  "dialyxir": {:hex, :dialyxir, "1.0.0-rc.4", "71b42f5ee1b7628f3e3a6565f4617dfb02d127a0499ab3e72750455e986df001", [:mix], [{:erlex, "~> 0.1", [hex: :erlex, repo: "hexpm", optional: false]}], "hexpm"},
   "earmark": {:hex, :earmark, "1.2.5", "4d21980d5d2862a2e13ec3c49ad9ad783ffc7ca5769cf6ff891a4553fbaae761", [:mix], [], "hexpm"},
+  "erlex": {:hex, :erlex, "0.1.6", "c01c889363168d3fdd23f4211647d8a34c0f9a21ec726762312e08e083f3d47e", [:mix], [], "hexpm"},
   "ex_doc": {:hex, :ex_doc, "0.19.1", "519bb9c19526ca51d326c060cb1778d4a9056b190086a8c6c115828eaccea6cf", [:mix], [{:earmark, "~> 1.1", [hex: :earmark, repo: "hexpm", optional: false]}, {:makeup_elixir, "~> 0.7", [hex: :makeup_elixir, repo: "hexpm", optional: false]}], "hexpm"},
   "makeup": {:hex, :makeup, "0.5.1", "966c5c2296da272d42f1de178c1d135e432662eca795d6dc12e5e8787514edf7", [:mix], [{:nimble_parsec, "~> 0.2.2", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm"},
   "makeup_elixir": {:hex, :makeup_elixir, "0.8.0", "1204a2f5b4f181775a0e456154830524cf2207cf4f9112215c05e0b76e4eca8b", [:mix], [{:makeup, "~> 0.5.0", [hex: :makeup, repo: "hexpm", optional: false]}, {:nimble_parsec, "~> 0.2.2", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm"},