diff --git a/lib/ex_aws/config.ex b/lib/ex_aws/config.ex
index fe608f32..4a54f9b1 100644
--- a/lib/ex_aws/config.ex
+++ b/lib/ex_aws/config.ex
@@ -38,11 +38,14 @@ defmodule ExAws.Config do
 
   def retrieve_runtime_config(%{config: config} = client) do
     new_config = config
-    |> Enum.reduce(%{}, fn {k, v}, config ->
-      case retrieve_runtime_value(v, client) do
-        %{} = result -> Map.merge(config, result)
-        value -> Map.put(config, k, value)
-      end
+    |> Enum.reduce(%{}, fn
+      {:host, host}, config ->
+        Map.put(config, :host, host)
+      {k, v}, config ->
+        case retrieve_runtime_value(v, client) do
+          %{} = result -> Map.merge(config, result)
+          value -> Map.put(config, k, value)
+        end
     end)
 
     %{client | config: new_config}
diff --git a/mix.exs b/mix.exs
index e9f9ab47..f525d8d4 100644
--- a/mix.exs
+++ b/mix.exs
@@ -3,7 +3,7 @@ defmodule ExAws.Mixfile do
 
   def project do
     [app: :ex_aws,
-     version: "0.4.11",
+     version: "0.4.12",
      elixir: "~> 1.0",
      description: "AWS client. Currently supports Dynamo, Kinesis, Lambda, S3, SQS",
      name: "ExAws",