diff --git a/gems/aws-sdk-core/lib/aws-sdk-core.rb b/gems/aws-sdk-core/lib/aws-sdk-core.rb
index bebc5af8621..d56146758e7 100644
--- a/gems/aws-sdk-core/lib/aws-sdk-core.rb
+++ b/gems/aws-sdk-core/lib/aws-sdk-core.rb
@@ -110,6 +110,7 @@ def shared_config
     def config=(config)
       if Hash === config
         @config = config
+        Aws.config.update({region: ENV['AWS_REGION']}) unless Aws.config.has_key?(:region)
       else
         raise ArgumentError, 'configuration object must be a hash'
       end