diff --git a/.credo.exs b/.credo.exs
index 7b89a30f..89090371 100644
--- a/.credo.exs
+++ b/.credo.exs
@@ -30,11 +30,6 @@
       #
       requires: [],
       #
-      # Credo automatically checks for updates, like e.g. Hex does.
-      # You can disable this behaviour below:
-      #
-      check_for_updates: true,
-      #
       # If you want to enforce a style guide and need a more traditional linting
       # experience, you can change `strict` to `true` below:
       #
@@ -60,13 +55,13 @@
         {Credo.Check.Consistency.SpaceInParentheses},
         {Credo.Check.Consistency.TabsOrSpaces},
 
-        # For some checks, like AliasUsage, you can only customize the priority
+        # You can customize the priority of any check
         # Priority values are: `low, normal, high, higher`
         #
         {Credo.Check.Design.AliasUsage, priority: :low},
 
-        # For others you can set parameters
-
+        # For some checks, you can also set other parameters
+        #
         # If you don't want the `setup` and `test` macro calls in ExUnit tests
         # or the `schema` macro in Ecto schemas to trigger DuplicatedCode, just
         # set the `excluded_macros` parameter to `[:schema, :setup, :test]`.
@@ -111,6 +106,7 @@
         {Credo.Check.Refactor.UnlessWithElse},
 
         {Credo.Check.Warning.BoolOperationOnSameValues},
+        {Credo.Check.Warning.ExpensiveEmptyEnumCheck},
         {Credo.Check.Warning.IExPry},
         {Credo.Check.Warning.IoInspect},
         {Credo.Check.Warning.LazyLogging},
diff --git a/.travis.yml b/.travis.yml
index 71f402ff..478133ef 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -8,9 +8,9 @@ cache:
     - _build
 matrix:
   include:
-    - elixir: 1.7.3
-      otp_release: 21.0
-    - elixir: 1.6.2
+    - elixir: 1.7.4
+      otp_release: 21.1
+    - elixir: 1.6.6
       otp_release: 20.2
     - elixir: 1.5.3
       otp_release: 20.2
@@ -33,4 +33,5 @@ before_script:
   - IP_IFACE=eth0 ./scripts/docker_up.sh
 script:
   - MIX_ENV=test mix deps.compile
+  - MIX_ENV=test mix compile --warnings-as-errors
   - ./scripts/ci_tests.sh
diff --git a/lib/kafka_ex/api_versions.ex b/lib/kafka_ex/api_versions.ex
index f29cc3ec..2328eb3a 100644
--- a/lib/kafka_ex/api_versions.ex
+++ b/lib/kafka_ex/api_versions.ex
@@ -1,26 +1,33 @@
 defmodule KafkaEx.ApiVersions do
+  @moduledoc false
 
   def api_versions_map(api_versions) do
     api_versions
     |> Enum.reduce(%{}, fn version, version_map ->
-        version_map |> Map.put(version.api_key, version)
-      end)
+      version_map |> Map.put(version.api_key, version)
+    end)
   end
 
-
-  def find_api_version(api_versions_map, message_type, {min_implemented_version, max_implemented_version}) do
+  def find_api_version(
+        api_versions_map,
+        message_type,
+        {min_implemented_version, max_implemented_version}
+      ) do
     if api_versions_map == [:unsupported] do
       {:ok, min_implemented_version}
     else
       case KafkaEx.Protocol.api_key(message_type) do
-        nil -> :unknown_message_for_client
-        api_key ->  case api_versions_map[api_key] do
-                      %{min_version: min} when min > max_implemented_version -> :no_version_supported
-                      %{max_version: max} when max < min_implemented_version -> :no_version_supported
-                      %{max_version: max} -> {:ok, Enum.min([max_implemented_version, max])}
-                      _ -> :unknown_message_for_server
-                    end
+        nil ->
+          :unknown_message_for_client
+
+        api_key ->
+          case api_versions_map[api_key] do
+            %{min_version: min} when min > max_implemented_version -> :no_version_supported
+            %{max_version: max} when max < min_implemented_version -> :no_version_supported
+            %{max_version: max} -> {:ok, Enum.min([max_implemented_version, max])}
+            _ -> :unknown_message_for_server
+          end
       end
     end
   end
-end
\ No newline at end of file
+end
diff --git a/lib/kafka_ex/protocol/api_versions.ex b/lib/kafka_ex/protocol/api_versions.ex
index 8ccc4938..1c1cb58d 100644
--- a/lib/kafka_ex/protocol/api_versions.ex
+++ b/lib/kafka_ex/protocol/api_versions.ex
@@ -56,7 +56,7 @@ defmodule KafkaEx.Protocol.ApiVersions do
                         api_versions_count :: 32-signed,
                         rest :: binary
                       >>, this_api_version) do
-    %{ parse_rest_of_response(api_versions_count, rest, this_api_version) | error_code: Protocol.error(error_code) }
+    %{parse_rest_of_response(api_versions_count, rest, this_api_version) | error_code: Protocol.error(error_code)}
   end
 
   defp parse_rest_of_response(api_versions_count, data, this_api_version) do
@@ -69,7 +69,7 @@ defmodule KafkaEx.Protocol.ApiVersions do
   end
 
   defp parse_one_api_version(<< api_key :: 16-signed, min_version :: 16-signed, max_version :: 16-signed, rest :: binary >>) do
-    {%ApiVersion{ api_key: api_key, min_version: min_version, max_version: max_version }, rest}
+    {%ApiVersion{api_key: api_key, min_version: min_version, max_version: max_version}, rest}
   end
 
 end
diff --git a/lib/kafka_ex/protocol/create_topics.ex b/lib/kafka_ex/protocol/create_topics.ex
index 4a37ce51..315703cb 100644
--- a/lib/kafka_ex/protocol/create_topics.ex
+++ b/lib/kafka_ex/protocol/create_topics.ex
@@ -1,8 +1,6 @@
-
 defmodule KafkaEx.Protocol.CreateTopics do
   alias KafkaEx.Protocol
   @supported_versions_range {0, 0}
-  @default_api_version 0
 
   @moduledoc """
   Implementation of the Kafka CreateTopics request and response APIs
@@ -24,16 +22,19 @@ defmodule KafkaEx.Protocol.CreateTopics do
   # timeout => INT32
 
   defmodule ReplicaAssignment do
+    @moduledoc false
     defstruct partition: nil, replicas: nil
-    @type t :: %ReplicaAssignment{ partition: integer, replicas: [integer] }
+    @type t :: %ReplicaAssignment{partition: integer, replicas: [integer]}
   end
 
   defmodule ConfigEntry do
+    @moduledoc false
     defstruct config_name: nil, config_value: nil
-    @type t :: %ConfigEntry{ config_name: binary, config_value: binary | nil }
+    @type t :: %ConfigEntry{config_name: binary, config_value: binary | nil}
   end
 
   defmodule TopicRequest do
+    @moduledoc false
     defstruct topic: nil,
               num_partitions: -1,
               replication_factor: -1,
@@ -55,8 +56,9 @@ defmodule KafkaEx.Protocol.CreateTopics do
   end
 
   defmodule TopicError do
+    @moduledoc false
     defstruct topic_name: nil, error_code: nil
-    @type t :: %TopicError{ topic_name: binary, error_code: atom }
+    @type t :: %TopicError{topic_name: binary, error_code: atom}
   end
 
   defmodule Response do
@@ -127,7 +129,7 @@ defmodule KafkaEx.Protocol.CreateTopics do
   end
 
   defp map_encode(elems, function) do
-    if nil == elems or 0 == length(elems) do
+    if nil == elems or [] == elems do
       << 0 ::  32-signed >>
     else
       << length(elems) ::  32-signed >> <>
@@ -138,15 +140,13 @@ defmodule KafkaEx.Protocol.CreateTopics do
   end
 
   @spec parse_response(binary, integer) :: [] | Response.t
-  def parse_response(message, api_version)
-
   def parse_response(<< _correlation_id :: 32-signed, topic_errors_count :: 32-signed, topic_errors :: binary >>, 0) do
     %Response{topic_errors: parse_topic_errors(topic_errors_count, topic_errors)}
   end
 
+  @spec parse_topic_errors(integer, binary) :: [TopicError.t]
   defp parse_topic_errors(0, _), do: []
 
-  @spec parse_topic_errors(integer, binary) :: [TopicError.t]
   defp parse_topic_errors(topic_errors_count,
       << topic_name_size :: 16-signed, topic_name :: size(topic_name_size)-binary, error_code :: 16-signed, rest :: binary >>) do
     [%TopicError{topic_name: topic_name, error_code: Protocol.error(error_code)} | parse_topic_errors(topic_errors_count - 1, rest)]
diff --git a/lib/kafka_ex/protocol/metadata.ex b/lib/kafka_ex/protocol/metadata.ex
index d790d151..c51a4f61 100644
--- a/lib/kafka_ex/protocol/metadata.ex
+++ b/lib/kafka_ex/protocol/metadata.ex
@@ -20,7 +20,7 @@ defmodule KafkaEx.Protocol.Metadata do
     alias KafkaEx.Socket
 
     defstruct node_id: -1, host: "", port: 0, socket: nil, is_controller: nil
-    @type t :: %__MODULE__{node_id: integer, host: binary, port: integer, socket: KafkaEx.Socket.t, is_controller: boolean }
+    @type t :: %__MODULE__{node_id: integer, host: binary, port: integer, socket: KafkaEx.Socket.t, is_controller: boolean}
 
     def connected?(%Broker{} = broker) do
       broker.socket != nil && Socket.open?(broker.socket)
@@ -197,7 +197,7 @@ defmodule KafkaEx.Protocol.Metadata do
           partition_metadatas_size :: 32-signed,
           rest :: binary >>) do
     {partition_metadatas, rest} = parse_partition_metadatas(partition_metadatas_size, [], rest)
-    [%TopicMetadata{error_code: Protocol.error(error_code), topic: topic, partition_metadatas: partition_metadatas, is_internal: is_internal == 1 } |
+    [%TopicMetadata{error_code: Protocol.error(error_code), topic: topic, partition_metadatas: partition_metadatas, is_internal: is_internal == 1} |
       parse_topic_metadatas_v1(topic_metadatas_size - 1, rest)]
   end
 
diff --git a/lib/kafka_ex/server.ex b/lib/kafka_ex/server.ex
index 71413ffe..ba629cc2 100644
--- a/lib/kafka_ex/server.ex
+++ b/lib/kafka_ex/server.ex
@@ -160,7 +160,7 @@ defmodule KafkaEx.Server do
     {:noreply, new_state, timeout | :hibernate} |
     {:stop, reason, reply, new_state} |
     {:stop, reason, new_state} when reply: term, new_state: term, reason: term
-  @callback kafka_create_topics(CreateTopicsRequest.t, network_timeout :: integer, state :: State.t) ::
+  @callback kafka_create_topics([CreateTopicsRequest.t], network_timeout :: integer, state :: State.t) ::
     {:reply, reply, new_state} when reply: term, new_state: term
   @callback kafka_api_versions(state :: State.t) ::
     {:reply, reply, new_state} when reply: term, new_state: term
@@ -312,6 +312,7 @@ defmodule KafkaEx.Server do
         end
       end
 
+      # credo:disable-for-next-line Credo.Check.Refactor.CyclomaticComplexity
       def kafka_server_produce_send_request(correlation_id, produce_request, produce_request_data, state) do
         {broker, state, corr_id} = case MetadataResponse.broker_for_topic(state.metadata, state.brokers, produce_request.topic, produce_request.partition) do
           nil ->
@@ -414,6 +415,12 @@ defmodule KafkaEx.Server do
         retrieve_metadata_with_version(brokers, correlation_id, sync_timeout, topic, retry, error_code, api_version)
       end
 
+      # credo:disable-for-next-line Credo.Check.Refactor.FunctionArity
+      def retrieve_metadata_with_version(_, correlation_id, _sync_timeout, topic, 0, error_code, server_api_versions) do
+        Logger.log(:error, "Metadata request for topic #{inspect topic} failed with error_code #{inspect error_code}")
+        {correlation_id, %Metadata.Response{}}
+      end
+
       # credo:disable-for-next-line Credo.Check.Refactor.FunctionArity
       def retrieve_metadata_with_version(brokers, correlation_id, sync_timeout, topic, retry, _error_code, api_version) do
         metadata_request = Metadata.create_request(correlation_id, @client_id, topic, api_version)
@@ -434,12 +441,6 @@ defmodule KafkaEx.Server do
         end
       end
 
-      # credo:disable-for-next-line Credo.Check.Refactor.FunctionArity
-      def retrieve_metadata_with_version(_, correlation_id, _sync_timeout, topic, 0, error_code, server_api_versions) do
-        Logger.log(:error, "Metadata request for topic #{inspect topic} failed with error_code #{inspect error_code}")
-        {correlation_id, %Metadata.Response{}}
-      end
-
 
       defoverridable [
         kafka_server_produce: 2, kafka_server_offset: 4,
diff --git a/lib/kafka_ex/server_0_p_10_and_later.ex b/lib/kafka_ex/server_0_p_10_and_later.ex
index 8d6d17d4..61f96879 100644
--- a/lib/kafka_ex/server_0_p_10_and_later.ex
+++ b/lib/kafka_ex/server_0_p_10_and_later.ex
@@ -65,7 +65,7 @@ defmodule KafkaEx.Server0P10AndLater do
 
     brokers = Enum.map(uris, fn({host, port}) -> %Broker{host: host, port: port, socket: NetworkClient.create_socket(host, port, ssl_options, use_ssl)} end)
 
-    { _, %KafkaEx.Protocol.ApiVersions.Response{ api_versions: api_versions, error_code: :no_error }, state } = kafka_api_versions(%State{brokers: brokers})
+    {_, %KafkaEx.Protocol.ApiVersions.Response{api_versions: api_versions, error_code: :no_error}, state} = kafka_api_versions(%State{brokers: brokers})
     api_versions = KafkaEx.ApiVersions.api_versions_map(api_versions)
 
     {correlation_id, metadata} = retrieve_metadata(brokers, state.correlation_id, config_sync_timeout(), [], api_versions)
@@ -116,7 +116,7 @@ defmodule KafkaEx.Server0P10AndLater do
               |> first_broker_response(state)
               |> ApiVersions.parse_response
 
-    {:reply, response, %{ state | correlation_id: state.correlation_id + 1 }}
+    {:reply, response, %{state | correlation_id: state.correlation_id + 1}}
   end
 
   def kafka_create_topics(requests, network_timeout, state) do
@@ -130,7 +130,7 @@ defmodule KafkaEx.Server0P10AndLater do
       timeout: network_timeout
     }
 
-    mainRequest = CreateTopics.create_request(state.correlation_id, @client_id, create_topics_request, api_version)
+    main_request = CreateTopics.create_request(state.correlation_id, @client_id, create_topics_request, api_version)
 
     broker = state.brokers |> Enum.find(&(&1.is_controller))
 
@@ -140,7 +140,7 @@ defmodule KafkaEx.Server0P10AndLater do
         {:topic_not_found, state}
       _ ->
         response = broker
-          |> NetworkClient.send_sync_request(mainRequest, config_sync_timeout())
+          |> NetworkClient.send_sync_request(main_request, config_sync_timeout())
           |> case do
                 {:error, reason} -> {:error, reason}
                 response -> CreateTopics.parse_response(response, api_version)
diff --git a/lib/kafka_ex/server_0_p_8_p_0.ex b/lib/kafka_ex/server_0_p_8_p_0.ex
index a359f63b..fc36edbe 100644
--- a/lib/kafka_ex/server_0_p_8_p_0.ex
+++ b/lib/kafka_ex/server_0_p_8_p_0.ex
@@ -15,6 +15,7 @@ defmodule KafkaEx.Server0P8P0 do
     {:nowarn_function, kafka_server_offset_commit: 2},
     {:nowarn_function, kafka_server_offset_fetch: 2},
     {:nowarn_function, kafka_create_topics: 3},
+    {:nowarn_function, kafka_api_versions: 1}
   ]
 
   use KafkaEx.Server
diff --git a/lib/kafka_ex/server_0_p_8_p_2.ex b/lib/kafka_ex/server_0_p_8_p_2.ex
index ee4b97d1..ae000e5c 100644
--- a/lib/kafka_ex/server_0_p_8_p_2.ex
+++ b/lib/kafka_ex/server_0_p_8_p_2.ex
@@ -10,6 +10,7 @@ defmodule KafkaEx.Server0P8P2 do
     {:nowarn_function, kafka_server_join_group: 3},
     {:nowarn_function, kafka_server_leave_group: 3},
     {:nowarn_function, kafka_create_topics: 3},
+    {:nowarn_function, kafka_api_versions: 1}
   ]
 
   use KafkaEx.Server
diff --git a/lib/kafka_ex/server_0_p_9_p_0.ex b/lib/kafka_ex/server_0_p_9_p_0.ex
index 20312e3b..87f6336a 100644
--- a/lib/kafka_ex/server_0_p_9_p_0.ex
+++ b/lib/kafka_ex/server_0_p_9_p_0.ex
@@ -7,6 +7,7 @@ defmodule KafkaEx.Server0P9P0 do
   # these functions aren't implemented for 0.9.0
   @dialyzer [
     {:nowarn_function, kafka_create_topics: 3},
+    {:nowarn_function, kafka_api_versions: 1}
   ]
 
   use KafkaEx.Server
@@ -46,7 +47,7 @@ defmodule KafkaEx.Server0P9P0 do
   defdelegate kafka_server_consumer_group_metadata(state), to: Server0P8P2
   defdelegate kafka_server_update_consumer_metadata(state), to: Server0P8P2
   defdelegate kafka_api_versions(state), to: Server0P8P2
-  defdelegate kafka_create_topics(requests, network_timeout, state),to: Server0P8P2
+  defdelegate kafka_create_topics(requests, network_timeout, state), to: Server0P8P2
 
   def kafka_server_init([args]) do
     kafka_server_init([args, self()])