diff --git a/lib/woocommerce_api.rb b/lib/woocommerce_api.rb
index 4ef29b2..20db6f8 100644
--- a/lib/woocommerce_api.rb
+++ b/lib/woocommerce_api.rb
@@ -132,10 +132,9 @@ def do_request method, endpoint, data = {}
       options = options.merge(@httparty_args)
 
       # Set headers.
-      options[:headers] = {
-        "User-Agent" => "WooCommerce API Client-Ruby/#{WooCommerce::VERSION}",
-        "Accept" => "application/json"
-      }
+      options[:headers] ||= {}
+      options[:headers]["User-Agent"] ||= "WooCommerce API Client-Ruby/#{WooCommerce::VERSION}"
+      options[:headers]["Accept"] = "application/json"
       options[:headers]["Content-Type"] = "application/json;charset=utf-8" if !data.empty?
 
       # Set basic authentication.