diff --git a/.gitignore b/.gitignore
index c10e56d..b45fdb9 100644
--- a/.gitignore
+++ b/.gitignore
@@ -25,3 +25,7 @@ erl_crash.dump
 # Directories that get created during tests
 /test/projects/**/_build
 /test/projects/**/deps
+
+# Dialyzer files
+/priv/plts/*.plt
+/priv/plts/*.plt.hash
diff --git a/lib/uniform.ex b/lib/uniform.ex
index dfa753e..35b6f7a 100644
--- a/lib/uniform.ex
+++ b/lib/uniform.ex
@@ -125,7 +125,7 @@ defmodule Uniform do
        disk the ejected app will be written, etc.). If there is a mistake, the user will
        have a chance to abort before performing a potentially destructive action.
        """ && false
-  @spec prepare(init :: %{name: atom, opts: [prepare_opt]}) :: Uniform.App.t()
+  @spec prepare(init :: %{name: String.t(), opts: [prepare_opt]}) :: Uniform.App.t()
   def prepare(%{name: name, opts: opts}) do
     # ensure the name was passed in under_score format; otherwise subtle bugs happen
     unless name in Uniform.ejectable_app_names() do
diff --git a/lib/uniform/app.ex b/lib/uniform/app.ex
index d532950..eac1819 100644
--- a/lib/uniform/app.ex
+++ b/lib/uniform/app.ex
@@ -230,7 +230,7 @@ defmodule Uniform.App do
 
   # Given a manifest struct, returns a `%Deps{}` struct containing
   # information about lib and mix dependencies.
-  @spec deps(Config.t(), Manifest.t()) :: t
+  @spec deps(Config.t(), Manifest.t()) :: Deps.t()
   defp deps(config, manifest) do
     all_libs = Config.lib_deps(config)
     all_mixs = Config.mix_deps(config)
diff --git a/lib/uniform/file.ex b/lib/uniform/file.ex
index 756615c..23d27e8 100644
--- a/lib/uniform/file.ex
+++ b/lib/uniform/file.ex
@@ -185,7 +185,7 @@ defmodule Uniform.File do
   # Given a directory, return which paths to eject based on the rules
   # associated with that directory. Includes files in `lib/<lib_dir>`
   # as well as `test/<lib_dir>`
-  @spec lib_dir_files(App.t(), String.t(), keyword) :: [Uniform.File.t()]
+  @spec lib_dir_files(App.t(), String.t(), keyword | map) :: [Uniform.File.t()]
   defp lib_dir_files(app, lib_dir, opts) do
     # location of lib and test cp_r is configurable for testing
     only = opts[:only]
diff --git a/mix.exs b/mix.exs
index 47a0425..9860024 100644
--- a/mix.exs
+++ b/mix.exs
@@ -12,6 +12,11 @@ defmodule Uniform.MixProject do
       start_permanent: Mix.env() == :prod,
       deps: deps(),
       elixirc_paths: elixirc_paths(Mix.env()),
+      dialyzer: [
+        plt_add_apps: [:mix],
+        plt_file: {:no_warn, "priv/plts/dialyzer.plt"},
+        list_unused_filters: true
+      ],
 
       # Hex
       description: "Write less boilerplate and reuse more code in your portfolio of Elixir apps",
@@ -30,7 +35,8 @@ defmodule Uniform.MixProject do
   defp deps do
     [
       {:ex_doc, ">= 0.30.9", only: [:dev, :docs], runtime: false},
-      {:sourceror, "~> 0.14"}
+      {:sourceror, "~> 0.14"},
+      {:dialyxir, "~> 1.4", only: [:dev, :test], runtime: false, optional: true}
     ]
   end
 
diff --git a/mix.lock b/mix.lock
index 9790cbc..e8d8dd3 100644
--- a/mix.lock
+++ b/mix.lock
@@ -1,5 +1,7 @@
 %{
+  "dialyxir": {:hex, :dialyxir, "1.4.2", "764a6e8e7a354f0ba95d58418178d486065ead1f69ad89782817c296d0d746a5", [:mix], [{:erlex, ">= 0.2.6", [hex: :erlex, repo: "hexpm", optional: false]}], "hexpm", "516603d8067b2fd585319e4b13d3674ad4f314a5902ba8130cd97dc902ce6bbd"},
   "earmark_parser": {:hex, :earmark_parser, "1.4.37", "2ad73550e27c8946648b06905a57e4d454e4d7229c2dafa72a0348c99d8be5f7", [:mix], [], "hexpm", "6b19783f2802f039806f375610faa22da130b8edc21209d0bff47918bb48360e"},
+  "erlex": {:hex, :erlex, "0.2.6", "c7987d15e899c7a2f34f5420d2a2ea0d659682c06ac607572df55a43753aa12e", [:mix], [], "hexpm", "2ed2e25711feb44d52b17d2780eabf998452f6efda104877a3881c2f8c0c0c75"},
   "ex_doc": {:hex, :ex_doc, "0.30.9", "d691453495c47434c0f2052b08dd91cc32bc4e1a218f86884563448ee2502dd2", [:mix], [{:earmark_parser, "~> 1.4.31", [hex: :earmark_parser, repo: "hexpm", optional: false]}, {:makeup_elixir, "~> 0.14", [hex: :makeup_elixir, repo: "hexpm", optional: false]}, {:makeup_erlang, "~> 0.1", [hex: :makeup_erlang, repo: "hexpm", optional: false]}], "hexpm", "d7aaaf21e95dc5cddabf89063327e96867d00013963eadf2c6ad135506a8bc10"},
   "makeup": {:hex, :makeup, "1.1.0", "6b67c8bc2882a6b6a445859952a602afc1a41c2e08379ca057c0f525366fc3ca", [:mix], [{:nimble_parsec, "~> 1.2.2 or ~> 1.3", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "0a45ed501f4a8897f580eabf99a2e5234ea3e75a4373c8a52824f6e873be57a6"},
   "makeup_elixir": {:hex, :makeup_elixir, "0.16.1", "cc9e3ca312f1cfeccc572b37a09980287e243648108384b97ff2b76e505c3555", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}, {:nimble_parsec, "~> 1.2.3 or ~> 1.3", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "e127a341ad1b209bd80f7bd1620a15693a9908ed780c3b763bccf7d200c767c6"},