diff --git a/lib/hyperwallet/api/client.rb b/lib/hyperwallet/api/client.rb
index fa58c5b..f931e9d 100644
--- a/lib/hyperwallet/api/client.rb
+++ b/lib/hyperwallet/api/client.rb
@@ -47,8 +47,8 @@ def request_url_for(resource)
     base_url + "/" + resource
   end
 
-  def base_url 
-    active_url + API_VERSION
+  def base_url
+    active_url + self.class.superclass.api_version
   end
 
   def active_url
diff --git a/lib/hyperwallet/api/config.rb b/lib/hyperwallet/api/config.rb
index 1ce9719..8f12a59 100644
--- a/lib/hyperwallet/api/config.rb
+++ b/lib/hyperwallet/api/config.rb
@@ -2,11 +2,11 @@ module Hyperwallet
   module Api
     class Config
 
-      PRODUCTION_URL     = "https://api.paylution.com/rest"
-      UAT_URL            = "https://uat-api.paylution.com/rest"
-
-      API_VERSION = "/v3"
-      MODES       = [:uat, :production]
+      PRODUCTION_URL         = "https://api.paylution.com/rest"
+      UAT_URL                = "https://uat-api.paylution.com/rest"
+      PRODUCTION_API_VERSION = "/v3"
+      UAT_API_VERSION        = "/v4"
+      MODES                  = [:uat, :production]
 
       class << self
         attr_accessor :api_user, :api_password, :api_mode, :proxy
@@ -17,6 +17,12 @@ def uat?
         def production?
           api_mode == :production
         end
+
+        def api_version
+          return PRODUCTION_API_VERSION if production?
+
+          UAT_API_VERSION
+        end
       end
     end
   end