diff --git a/mix.exs b/mix.exs
index b4717669f9..c62ea854d1 100644
--- a/mix.exs
+++ b/mix.exs
@@ -82,6 +82,7 @@ defmodule Absinthe.Mixfile do
       {:ex_doc, "~> 0.22", only: :dev},
       {:benchee, ">= 1.0.0", only: :dev},
       {:dialyxir, "~> 1.1", only: [:dev, :test], runtime: false},
+      {:jason, "~> 1.0", only: :test, runtime: false},
       {:mix_test_watch, "~> 1.0", only: :dev, runtime: false},
       {:makeup_graphql, "~> 0.1.0", only: :dev}
     ]
diff --git a/mix.lock b/mix.lock
index 472f9ca11d..a6fe4bb996 100644
--- a/mix.lock
+++ b/mix.lock
@@ -8,6 +8,7 @@
   "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"},
   "file_system": {:hex, :file_system, "0.2.10", "fb082005a9cd1711c05b5248710f8826b02d7d1784e7c3451f9c1231d4fc162d", [:mix], [], "hexpm", "41195edbfb562a593726eda3b3e8b103a309b733ad25f3d642ba49696bf715dc"},
+  "jason": {:hex, :jason, "1.4.4", "b9226785a9aa77b6857ca22832cffa5d5011a667207eb2a0ad56adb5db443b8a", [:mix], [{:decimal, "~> 1.0 or ~> 2.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm", "c5eb0cab91f094599f94d55bc63409236a8ec69a21a67814529e8d5f6cc90b3b"},
   "makeup": {:hex, :makeup, "1.1.1", "fa0bc768698053b2b3869fa8a62616501ff9d11a562f3ce39580d60860c3a55e", [:mix], [{:nimble_parsec, "~> 1.2.2 or ~> 1.3", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "5dc62fbdd0de44de194898b6710692490be74baa02d9d108bc29f007783b0b48"},
   "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"},
   "makeup_erlang": {:hex, :makeup_erlang, "0.1.2", "ad87296a092a46e03b7e9b0be7631ddcf64c790fa68a9ef5323b6cbb36affc72", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}], "hexpm", "f3f5a1ca93ce6e092d92b6d9c049bcda58a3b617a8d888f8e7231c85630e8108"},
diff --git a/priv/graphql/introspection.graphql b/priv/graphql/introspection.graphql
index 3f8b0fd5e9..62369e5839 100644
--- a/priv/graphql/introspection.graphql
+++ b/priv/graphql/introspection.graphql
@@ -41,7 +41,7 @@ fragment FullType on __Type {
     isDeprecated
     deprecationReason
   }
-  inputFields {
+  inputFields(includeDeprecated: true) {
     ...InputValue
   }
   interfaces {
diff --git a/test/mix/tasks/absinthe.schema.json_test.exs b/test/mix/tasks/absinthe.schema.json_test.exs
index d7081cbd42..b4ce25dc65 100644
--- a/test/mix/tasks/absinthe.schema.json_test.exs
+++ b/test/mix/tasks/absinthe.schema.json_test.exs
@@ -10,11 +10,28 @@ defmodule Mix.Tasks.Absinthe.Schema.JsonTest do
       field :item, :item
     end
 
+    mutation do
+      field :update_item,
+        type: :item,
+        args: [
+          id: [type: non_null(:string)],
+          item: [type: non_null(:input_item)]
+        ]
+    end
+
     object :item do
       description "A Basic Type"
       field :id, :id
       field :name, :string
     end
+
+    input_object :input_item do
+      description "A thing as input"
+      field :value, :integer
+      field :deprecated_field, :string, deprecate: true
+      field :deprecated_field_with_reason, :string, deprecate: "reason"
+      field :deprecated_non_null_field, non_null(:string), deprecate: true
+    end
   end
 
   defmodule PersistentTermTestSchema do
@@ -99,10 +116,33 @@ defmodule Mix.Tasks.Absinthe.Schema.JsonTest do
     test "generates a JSON file", %{tmp_dir: tmp_dir} do
       path = Path.join(tmp_dir, "schema.json")
 
-      argv = ["--schema", @test_schema, "--json-codec", @test_encoder, path]
+      argv = ["--schema", @test_schema, path]
       assert Task.run(argv)
 
       assert File.exists?(path)
+
+      decoded_schema = path |> File.read!() |> Jason.decode!()
+
+      # Includes deprecated fields by default
+      input_thing_field_names =
+        get_in(
+          decoded_schema,
+          [
+            "data",
+            "__schema",
+            "types",
+            Access.filter(&(&1["name"] == "InputItem")),
+            "inputFields",
+            Access.all(),
+            "name"
+          ]
+        )
+        |> List.flatten()
+
+      assert "value" in input_thing_field_names
+      assert "deprecatedField" in input_thing_field_names
+      assert "deprecatedFieldWithReason" in input_thing_field_names
+      assert "deprecatedNonNullField" in input_thing_field_names
     end
 
     @tag :tmp_dir