diff --git a/lib/ecto/json.ex b/lib/ecto/json.ex
index b28c5d462e..ac2a5b499a 100644
--- a/lib/ecto/json.ex
+++ b/lib/ecto/json.ex
@@ -1,48 +1,52 @@
-if Code.ensure_loaded?(Jason.Encoder) do
-  defimpl Jason.Encoder, for: Ecto.Association.NotLoaded do
-    def encode(%{__owner__: owner, __field__: field}, _) do
-      raise """
-      cannot encode association #{inspect(field)} from #{inspect(owner)} to \
-      JSON because the association was not loaded.
+for encoder <- [Jason.Encoder, JSON.Encoder] do
+  module = Macro.inspect_atom(:literal, encoder)
 
-      You can either preload the association:
+  if Code.ensure_loaded?(encoder) do
+    defimpl encoder, for: Ecto.Association.NotLoaded do
+      def encode(%{__owner__: owner, __field__: field}, _) do
+        raise """
+        cannot encode association #{inspect(field)} from #{inspect(owner)} to \
+        JSON because the association was not loaded.
 
-          Repo.preload(#{inspect(owner)}, #{inspect(field)})
+        You can either preload the association:
 
-      Or choose to not encode the association when converting the struct \
-      to JSON by explicitly listing the JSON fields in your schema:
+            Repo.preload(#{inspect(owner)}, #{inspect(field)})
 
-          defmodule #{inspect(owner)} do
-            # ...
+        Or choose to not encode the association when converting the struct \
+        to JSON by explicitly listing the JSON fields in your schema:
 
-            @derive {Jason.Encoder, only: [:name, :title, ...]}
-            schema ... do
+            defmodule #{inspect(owner)} do
+              # ...
 
-      You can also use the :except option instead of :only if you would \
-      prefer to skip some fields.
-      """
+              @derive {#{unquote(module)}, only: [:name, :title, ...]}
+              schema ... do
+
+        You can also use the :except option instead of :only if you would \
+        prefer to skip some fields.
+        """
+      end
     end
-  end
 
-  defimpl Jason.Encoder, for: Ecto.Schema.Metadata do
-    def encode(%{schema: schema}, _) do
-      raise """
-      cannot encode metadata from the :__meta__ field for #{inspect(schema)} \
-      to JSON. This metadata is used internally by Ecto and should never be \
-      exposed externally.
+    defimpl encoder, for: Ecto.Schema.Metadata do
+      def encode(%{schema: schema}, _) do
+        raise """
+        cannot encode metadata from the :__meta__ field for #{inspect(schema)} \
+        to JSON. This metadata is used internally by Ecto and should never be \
+        exposed externally.
 
-      You can either map the schemas to remove the :__meta__ field before \
-      encoding or explicitly list the JSON fields in your schema:
+        You can either map the schemas to remove the :__meta__ field before \
+        encoding or explicitly list the JSON fields in your schema:
 
-          defmodule #{inspect(schema)} do
-            # ...
+            defmodule #{inspect(schema)} do
+              # ...
 
-            @derive {Jason.Encoder, only: [:name, :title, ...]}
-            schema ... do
+              @derive {#{unquote(module)}, only: [:name, :title, ...]}
+              schema ... do
 
-      You can also use the :except option instead of :only if you would \
-      prefer to skip some fields.
-      """
+        You can also use the :except option instead of :only if you would \
+        prefer to skip some fields.
+        """
+      end
     end
   end
 end
diff --git a/mix.lock b/mix.lock
index 462cdbebf3..b85b92f4ef 100644
--- a/mix.lock
+++ b/mix.lock
@@ -1,5 +1,5 @@
 %{
-  "decimal": {:hex, :decimal, "2.1.1", "5611dca5d4b2c3dd497dec8f68751f1f1a54755e8ed2a966c2633cf885973ad6", [:mix], [], "hexpm", "53cfe5f497ed0e7771ae1a475575603d77425099ba5faef9394932b35020ffcc"},
+  "decimal": {:hex, :decimal, "2.3.0", "3ad6255aa77b4a3c4f818171b12d237500e63525c2fd056699967a3e7ea20f62", [:mix], [], "hexpm", "a4d66355cb29cb47c3cf30e71329e58361cfcb37c34235ef3bf1d7bf3773aeac"},
   "earmark_parser": {:hex, :earmark_parser, "1.4.41", "ab34711c9dc6212dda44fcd20ecb87ac3f3fce6f0ca2f28d4a00e4154f8cd599", [:mix], [], "hexpm", "a81a04c7e34b6617c2792e291b5a2e57ab316365c2644ddc553bb9ed863ebefa"},
   "ex_doc": {:hex, :ex_doc, "0.35.1", "de804c590d3df2d9d5b8aec77d758b00c814b356119b3d4455e4b8a8687aecaf", [:mix], [{:earmark_parser, "~> 1.4.39", [hex: :earmark_parser, repo: "hexpm", optional: false]}, {:makeup_c, ">= 0.1.0", [hex: :makeup_c, repo: "hexpm", optional: true]}, {:makeup_elixir, "~> 0.14 or ~> 1.0", [hex: :makeup_elixir, repo: "hexpm", optional: false]}, {:makeup_erlang, "~> 0.1 or ~> 1.0", [hex: :makeup_erlang, repo: "hexpm", optional: false]}, {:makeup_html, ">= 0.1.0", [hex: :makeup_html, repo: "hexpm", optional: true]}], "hexpm", "2121c6402c8d44b05622677b761371a759143b958c6c19f6558ff64d0aed40df"},
   "jason": {:hex, :jason, "1.4.1", "af1504e35f629ddcdd6addb3513c3853991f694921b1b9368b0bd32beb9f1b63", [:mix], [{:decimal, "~> 1.0 or ~> 2.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm", "fbb01ecdfd565b56261302f7e1fcc27c4fb8f32d56eab74db621fc154604a7a1"},
diff --git a/test/ecto/json_test.exs b/test/ecto/json_test.exs
index 5459902923..3e0b079213 100644
--- a/test/ecto/json_test.exs
+++ b/test/ecto/json_test.exs
@@ -1,29 +1,40 @@
 defmodule Ecto.JsonTest do
   use ExUnit.Case, async: true
 
+  @implementations [{Jason, Jason.Encoder}, {JSON, JSON.Encoder}]
+
+  loaded_implementations =
+    for {_lib, encoder} = implementation <- @implementations,
+        Code.ensure_loaded?(encoder),
+        do: implementation
+
   defmodule User do
     use Ecto.Schema
 
-    @derive Jason.Encoder
+    @derive Keyword.values(loaded_implementations)
     schema "users" do
       has_many :comments, Ecto.Comment
     end
   end
 
-  test "encodes decimal" do
-    decimal = Decimal.new("1.0")
-    assert Jason.encode!(decimal) == ~s("1.0")
-  end
+  for {json_library, _encoder} <- loaded_implementations do
+    describe to_string(json_library) do
+      test "encodes decimal" do
+        decimal = Decimal.new("1.0")
+        assert unquote(json_library).encode!(decimal) == ~s("1.0")
+      end
 
-  test "fails on association not loaded" do
-    assert_raise RuntimeError,
-                 ~r/cannot encode association :comments from Ecto.JsonTest.User to JSON/,
-                 fn -> Jason.encode!(%User{}.comments) end
-  end
+      test "fails on association not loaded" do
+        assert_raise RuntimeError,
+                     ~r/cannot encode association :comments from Ecto.JsonTest.User to JSON/,
+                     fn -> unquote(json_library).encode!(%User{}.comments) end
+      end
 
-  test "fails when encoding __meta__" do
-    assert_raise RuntimeError,
-                 ~r/cannot encode metadata from the :__meta__ field for Ecto.JsonTest.User to JSON/,
-                 fn -> Jason.encode!(%User{comments: []}) end
+      test "fails when encoding __meta__" do
+        assert_raise RuntimeError,
+                     ~r/cannot encode metadata from the :__meta__ field for Ecto.JsonTest.User to JSON/,
+                     fn -> unquote(json_library).encode!(%User{comments: []}) end
+      end
+    end
   end
 end