diff --git a/CHANGELOG b/CHANGELOG
index 17f4a81..d1606d2 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,6 +1,7 @@
 # 2.0.0 (unreleased)
   - BREAKING CHANGE: Remove generated defs/0 function
   - BREAKING CHANGE: Remove Protox.Encode.encode/1 and Protox.Encode.encode!/1
+  - BREAKING CHANGE: The JSON library is now configurable via the `:json_library` option at compile time
   - Drop support for Elixir < 1.15
 
 # 1.7.8
diff --git a/lib/protox.ex b/lib/protox.ex
index fc7c8f4..8bd45d0 100644
--- a/lib/protox.ex
+++ b/lib/protox.ex
@@ -159,32 +159,21 @@ defmodule Protox do
   - `input` could not be decoded to JSON; `reason` is a `Protox.JsonDecodingError` error
 
   ## JSON library configuration
-  The default library to decode JSON is [`Jason`](https://github.com/michalmuskala/jason).
-  However, you can chose to use [`Poison`](https://github.com/devinus/poison):
-      iex> Protox.json_decode("{\\"a\\":\\"BAR\\"}", Namespace.Fiz.Foo, json_decoder: Poison)
-      {:ok, %Namespace.Fiz.Foo{__uf__: [], a: :BAR, b: %{}}}
-
-  You can also use another library as long as it exports an `decode!` function. You can easily
-  create a module to wrap a library that would not have this interface (like [`jiffy`](https://github.com/davisp/jiffy)):
-      defmodule Jiffy do
-        def decode!(input) do
-          :jiffy.decode(input, [:return_maps, :use_nil])
-        end
-      end
+  TODO: document json library configuration
   """
-  @doc since: "1.6.0"
-  @spec json_decode(iodata(), atom(), keyword()) :: {:ok, struct()} | {:error, any()}
-  def json_decode(input, message_module, opts \\ []) do
-    message_module.json_decode(input, opts)
+  @doc since: "2.0.0"
+  @spec json_decode(iodata(), atom()) :: {:ok, struct()} | {:error, any()}
+  def json_decode(input, message_module) do
+    message_module.json_decode(input)
   end
 
   @doc """
   Throwing version of `json_decode/2`.
   """
-  @doc since: "1.6.0"
-  @spec json_decode!(iodata(), atom(), keyword()) :: struct() | no_return()
-  def json_decode!(input, message_module, opts \\ []) do
-    message_module.json_decode!(input, opts)
+  @doc since: "2.0.0"
+  @spec json_decode!(iodata(), atom()) :: struct() | no_return()
+  def json_decode!(input, message_module) do
+    message_module.json_decode!(input)
   end
 
   @doc """
@@ -211,36 +200,25 @@ defmodule Protox do
       "{\\"msgK\\":{\\"2\\":\\"bar\\",\\"1\\":\\"foo\\"}}"
 
   ## JSON library configuration
-  The default library to encode values (i.e. mostly to escape strings) to JSON  is [`Jason`](https://github.com/michalmuskala/jason).
-  However, you can chose to use [`Poison`](https://github.com/devinus/poison):
-      iex> msg = %Namespace.Fiz.Foo{a: :BAR}
-      iex> Protox.json_encode(msg, json_encoder: Poison)
-      {:ok, ["{", ["\\"a\\"", ":", "\\"BAR\\""], "}"]}
-
-  You can also use another library as long as it exports an `encode!` function, which is expected to return objects as maps and `nil`
-  to represent `null`.
-  You can easily create a module to wrap a library that would not have this interface (like [`jiffy`](https://github.com/davisp/jiffy)):
-      defmodule Jiffy do
-        defdelegate encode!(msg), to: :jiffy, as: :encode
-      end
+  TODO: document the json library configuration
 
   ## Encoding specifications
   See https://developers.google.com/protocol-buffers/docs/proto3#json for the specifications
   of the encoding.
   """
-  @doc since: "1.6.0"
-  @spec json_encode(struct(), keyword()) :: {:ok, iodata()} | {:error, any()}
-  def json_encode(msg, opts \\ []) do
-    msg.__struct__.json_encode(msg, opts)
+  @doc since: "2.0.0"
+  @spec json_encode(struct()) :: {:ok, iodata()} | {:error, any()}
+  def json_encode(msg) do
+    msg.__struct__.json_encode(msg)
   end
 
   @doc """
   Throwing version of `json_encode/1`.
   """
-  @doc since: "1.6.0"
-  @spec json_encode!(struct(), keyword()) :: iodata() | no_return()
-  def json_encode!(msg, opts \\ []) do
-    msg.__struct__.json_encode!(msg, opts)
+  @doc since: "2.0.0"
+  @spec json_encode!(struct()) :: iodata() | no_return()
+  def json_encode!(msg) do
+    msg.__struct__.json_encode!(msg)
   end
 
   # -- Private
diff --git a/lib/protox/define_message.ex b/lib/protox/define_message.ex
index 33613e5..348a653 100644
--- a/lib/protox/define_message.ex
+++ b/lib/protox/define_message.ex
@@ -5,6 +5,7 @@ defmodule Protox.DefineMessage do
 
   def define(messages, opts \\ []) do
     keep_unknown_fields = Keyword.get(opts, :keep_unknown_fields, true)
+    json_library = Keyword.get(opts, :json_library, Jason)
 
     for msg = %Protox.Message{} <- messages do
       fields = Enum.sort(msg.fields, &(&1.tag < &2.tag))
@@ -16,7 +17,7 @@ defmodule Protox.DefineMessage do
       unknown_fields_funs = make_unknown_fields_funs(unknown_fields, keep_unknown_fields)
       required_fields_fun = make_required_fields_fun(required_fields)
       fields_access_funs = make_fields_access_funs(fields)
-      json_funs = make_json_funs(msg.name)
+      json_funs = make_json_funs(msg.name, json_library)
       default_fun = make_default_funs(fields)
       syntax_fun = make_syntax_fun(msg.syntax)
       file_options_fun = make_file_options_fun(msg)
@@ -93,44 +94,42 @@ defmodule Protox.DefineMessage do
     end
   end
 
-  defp make_json_funs(msg_name) do
+  defp make_json_funs(msg_name, json_library) do
+    json_library_wrapper = Protox.JsonLibrary.get_wrapper(json_library)
+
     quote do
-      @spec json_decode(iodata(), keyword()) :: {:ok, struct()} | {:error, any()}
-      def json_decode(input, opts \\ []) do
+      @spec json_decode(iodata()) :: {:ok, struct()} | {:error, any()}
+      def json_decode(input) do
         try do
-          {:ok, json_decode!(input, opts)}
+          {:ok, json_decode!(input)}
         rescue
           e in Protox.JsonDecodingError ->
             {:error, e}
         end
       end
 
-      @spec json_decode!(iodata(), keyword()) :: struct() | no_return()
-      def json_decode!(input, opts \\ []) do
-        json_library_wrapper = Protox.JsonLibrary.get_library(opts, :decode)
-
+      @spec json_decode!(iodata()) :: struct() | no_return()
+      def json_decode!(input) do
         Protox.JsonDecode.decode!(
           input,
           unquote(msg_name),
-          &json_library_wrapper.decode!(&1)
+          &unquote(json_library_wrapper).decode!(&1)
         )
       end
 
-      @spec json_encode(struct(), keyword()) :: {:ok, iodata()} | {:error, any()}
-      def json_encode(msg, opts \\ []) do
+      @spec json_encode(struct()) :: {:ok, iodata()} | {:error, any()}
+      def json_encode(msg) do
         try do
-          {:ok, json_encode!(msg, opts)}
+          {:ok, json_encode!(msg)}
         rescue
           e in Protox.JsonEncodingError ->
             {:error, e}
         end
       end
 
-      @spec json_encode!(struct(), keyword()) :: iodata() | no_return()
-      def json_encode!(msg, opts \\ []) do
-        json_library_wrapper = Protox.JsonLibrary.get_library(opts, :encode)
-
-        Protox.JsonEncode.encode!(msg, &json_library_wrapper.encode!(&1))
+      @spec json_encode!(struct()) :: iodata() | no_return()
+      def json_encode!(msg) do
+        Protox.JsonEncode.encode!(msg, &unquote(json_library_wrapper).encode!(&1))
       end
     end
   end
diff --git a/lib/protox/errors.ex b/lib/protox/errors.ex
index 126571c..c9b9e5a 100644
--- a/lib/protox/errors.ex
+++ b/lib/protox/errors.ex
@@ -91,6 +91,21 @@ defmodule Protox.JsonEncodingError do
   end
 end
 
+defmodule Protox.JsonLibraryError do
+  @moduledoc """
+  This error is thrown when the configured JSON library is not available.
+  """
+
+  defexception message: ""
+
+  @doc false
+  def new() do
+    %__MODULE__{
+      message: "Cannot load JSON library. Please check your project dependencies."
+    }
+  end
+end
+
 defmodule Protox.RequiredFieldsError do
   @moduledoc """
   This error is thrown when encoding or decoding a Protobuf 2 message
diff --git a/lib/protox/jason.ex b/lib/protox/jason.ex
index 532eac3..fc9f53c 100644
--- a/lib/protox/jason.ex
+++ b/lib/protox/jason.ex
@@ -2,45 +2,23 @@ defmodule Protox.Jason do
   @moduledoc false
   @behaviour Protox.JsonLibrary
 
-  if Code.ensure_loaded?(Jason) do
-    @impl true
-    def load(), do: :ok
-
-    @impl true
-    def decode!(iodata) do
-      try do
-        Jason.decode!(iodata)
-      rescue
-        e in Jason.DecodeError ->
-          reraise Protox.JsonDecodingError.new(Exception.message(e)), __STACKTRACE__
-      end
-    end
-
-    @impl true
-    def encode!(term) do
-      try do
-        Jason.encode!(term)
-      rescue
-        e in Jason.EncodeError ->
-          reraise Protox.JsonEncodingError.new(Exception.message(e)), __STACKTRACE__
-      end
-    end
-  else
-    @impl true
-    def load(), do: :error
-
-    @impl true
-    def decode!(_iodata) do
-      raise Protox.JsonDecodingError.new(
-              "Jason library not loaded. Please check your project dependencies."
-            )
+  @impl true
+  def decode!(iodata) do
+    try do
+      Jason.decode!(iodata)
+    rescue
+      e in [Jason.DecodeError, Protocol.UndefinedError] ->
+        reraise Protox.JsonDecodingError.new(Exception.message(e)), __STACKTRACE__
     end
+  end
 
-    @impl true
-    def encode!(_term) do
-      raise Protox.JsonEncodingError.new(
-              "Jason library not loaded. Please check your project dependencies."
-            )
+  @impl true
+  def encode!(term) do
+    try do
+      Jason.encode!(term)
+    rescue
+      e in Jason.EncodeError ->
+        reraise Protox.JsonEncodingError.new(Exception.message(e)), __STACKTRACE__
     end
   end
 end
diff --git a/lib/protox/json_library.ex b/lib/protox/json_library.ex
index 3b9f394..cd6f4cd 100644
--- a/lib/protox/json_library.ex
+++ b/lib/protox/json_library.ex
@@ -3,8 +3,6 @@ defmodule Protox.JsonLibrary do
   The behaviour to implement when wrapping a JSON library.
   """
 
-  @callback load() :: :ok | :error
-
   @doc """
   Should wrap any exception of the underlying library in Protox.JsonDecodingError.
   """
@@ -16,21 +14,11 @@ defmodule Protox.JsonLibrary do
   @callback encode!(term()) :: iodata() | no_return()
 
   @doc false
-  def get_library(opts, decoding_or_encoding) do
-    json_library_name = Keyword.get(opts, :json_library, Jason)
-    json_library_wrapper = Module.concat(Protox, json_library_name)
-
-    case json_library_wrapper.load() do
-      :ok ->
-        json_library_wrapper
-
-      :error ->
-        message = "cannot load JSON library. Please check your project dependencies."
-
-        case decoding_or_encoding do
-          :decode -> raise Protox.JsonDecodingError.new(message)
-          :encode -> raise Protox.JsonEncodingError.new(message)
-        end
+  def get_wrapper(json_library) do
+    if Code.ensure_loaded?(json_library) do
+      Module.concat(Protox, json_library)
+    else
+      raise Protox.JsonLibraryError.new()
     end
   end
 end
diff --git a/lib/protox/poison.ex b/lib/protox/poison.ex
index 92e7111..d4fc3e6 100644
--- a/lib/protox/poison.ex
+++ b/lib/protox/poison.ex
@@ -2,45 +2,23 @@ defmodule Protox.Poison do
   @moduledoc false
   @behaviour Protox.JsonLibrary
 
-  if Code.ensure_loaded?(Poison) do
-    @impl true
-    def load(), do: :ok
-
-    @impl true
-    def decode!(iodata) do
-      try do
-        Poison.decode!(iodata)
-      rescue
-        e in [Poison.DecodeError, Poison.ParseError] ->
-          reraise Protox.JsonDecodingError.new(Exception.message(e)), __STACKTRACE__
-      end
-    end
-
-    @impl true
-    def encode!(term) do
-      try do
-        Poison.encode!(term)
-      rescue
-        e in Poison.EncodeError ->
-          reraise Protox.JsonEncodingError.new(Exception.message(e)), __STACKTRACE__
-      end
-    end
-  else
-    @impl true
-    def load(), do: :error
-
-    @impl true
-    def decode!(_iodata) do
-      raise Protox.JsonDecodingError.new(
-              "Poison library not loaded. Please check your project dependencies."
-            )
+  @impl true
+  def decode!(iodata) do
+    try do
+      Poison.decode!(iodata)
+    rescue
+      e in [Poison.DecodeError, Poison.ParseError] ->
+        reraise Protox.JsonDecodingError.new(Exception.message(e)), __STACKTRACE__
     end
+  end
 
-    @impl true
-    def encode!(_term) do
-      raise Protox.JsonEncodingError.new(
-              "Poison library not loaded. Please check your project dependencies."
-            )
+  @impl true
+  def encode!(term) do
+    try do
+      Poison.encode!(term)
+    rescue
+      e in Poison.EncodeError ->
+        reraise Protox.JsonEncodingError.new(Exception.message(e)), __STACKTRACE__
     end
   end
 end
diff --git a/test/protox/json_decode_test.exs b/test/protox/json_decode_test.exs
index badcf48..b548f8b 100644
--- a/test/protox/json_decode_test.exs
+++ b/test/protox/json_decode_test.exs
@@ -685,26 +685,24 @@ defmodule Protox.JsonDecodeTest do
       {
         :ok,
         %{
-          json: "{\"a\":null, \"b\":\"foo\", \"c\": 33}",
-          expected: %Sub{a: 0, b: "foo", c: 33}
+          json: "{\"a\":null, \"b\":\"foo\", \"c\": 33}"
         }
       }
     end
 
-    test "Success: jason", %{json: json, expected: expected} do
-      assert Protox.json_decode!(json, Sub, json_library: Jason) == expected
+    test "Success: Jason", %{json: json} do
+      assert Protox.json_decode!(json, WithJason.Sub) == %WithJason.Sub{a: 0, b: "foo", c: 33}
     end
 
-    test "Success: poison", %{json: json, expected: expected} do
-      assert Protox.json_decode!(json, Sub, json_library: Poison) == expected
+    test "Success: Poison", %{json: json} do
+      assert Protox.json_decode!(json, WithPoison.Sub) == %WithPoison.Sub{a: 0, b: "foo", c: 33}
     end
 
-    test "Failure: poison", %{} do
+    test "Failure: Poison", %{} do
       assert_raise Protox.JsonDecodingError, fn ->
         Protox.json_decode!(
           "{\"mapInt32Int32\": 1",
-          ProtobufTestMessages.Proto3.TestAllTypesProto3,
-          json_library: Poison
+          WithPoison.ProtobufTestMessages.Proto3.TestAllTypesProto3
         )
       end
     end
diff --git a/test/protox/json_encode_test.exs b/test/protox/json_encode_test.exs
index ae57397..ba8bbae 100644
--- a/test/protox/json_encode_test.exs
+++ b/test/protox/json_encode_test.exs
@@ -393,8 +393,8 @@ defmodule Protox.JsonEncodeTest do
 
   describe "JSON libraries" do
     test "Success: Jason" do
-      msg = %Msg{msg_k: %{1 => "a", 2 => "b"}}
-      json = Protox.json_encode!(msg, json_library: Jason)
+      msg = %WithJason.Msg{msg_k: %{1 => "a", 2 => "b"}}
+      json = Protox.json_encode!(msg)
 
       assert json == [
                "{",
@@ -404,8 +404,8 @@ defmodule Protox.JsonEncodeTest do
     end
 
     test "Success: Poison" do
-      msg = %Msg{msg_k: %{1 => "a", 2 => "b"}}
-      json = Protox.json_encode!(msg, json_library: Poison)
+      msg = %WithPoison.Msg{msg_k: %{1 => "a", 2 => "b"}}
+      json = Protox.json_encode!(msg)
 
       assert json == [
                "{",
@@ -415,10 +415,12 @@ defmodule Protox.JsonEncodeTest do
     end
 
     test "Failure: Poison" do
-      invalid_field = %ProtobufTestMessages.Proto3.TestAllTypesProto3{optional_int32: make_ref()}
+      invalid_field = %WithPoison.ProtobufTestMessages.Proto3.TestAllTypesProto3{
+        optional_int32: make_ref()
+      }
 
       assert_raise Protox.JsonEncodingError, fn ->
-        Protox.json_encode!(invalid_field, json_library: Poison)
+        Protox.json_encode!(invalid_field)
       end
     end
   end
diff --git a/test/support/messages.ex b/test/support/messages.ex
index 320766d..947f5ac 100644
--- a/test/support/messages.ex
+++ b/test/support/messages.ex
@@ -5,4 +5,20 @@ defmodule Protox.Messages do
     files: [
       "./test/samples/messages.proto"
     ]
+
+  use Protox,
+    files: [
+      "./test/samples/messages.proto",
+      "./test/samples/test_messages_proto3.proto"
+    ],
+    namespace: WithJason,
+    json_library: Jason
+
+  use Protox,
+    files: [
+      "./test/samples/messages.proto",
+      "./test/samples/test_messages_proto3.proto"
+    ],
+    namespace: WithPoison,
+    json_library: Poison
 end