diff --git a/app/models/spree/gateway_decorator.rb b/app/models/spree/gateway_decorator.rb
new file mode 100644
index 0000000000..e40b260ae8
--- /dev/null
+++ b/app/models/spree/gateway_decorator.rb
@@ -0,0 +1,10 @@
+Spree::Gateway.class_eval do
+
+  # Due to class load order, when config.cache_classes is enabled (ie. staging and production
+  # environments), this association isn't inherited from PaymentMethod. As a result, creating
+  # payment methods using payment gateways results in:
+  # undefined method `association_class' for nil:NilClass
+  # To avoid that, we redefine this association here.
+
+  has_and_belongs_to_many :distributors, join_table: 'distributors_payment_methods', :class_name => 'Enterprise', foreign_key: 'payment_method_id', association_foreign_key: 'distributor_id'
+end
diff --git a/app/models/spree/payment_method_decorator.rb b/app/models/spree/payment_method_decorator.rb
index 8e696989a4..ddbc0251a9 100644
--- a/app/models/spree/payment_method_decorator.rb
+++ b/app/models/spree/payment_method_decorator.rb
@@ -1,4 +1,5 @@
 Spree::PaymentMethod.class_eval do
+  # See gateway_decorator.rb when modifying this association
   has_and_belongs_to_many :distributors, join_table: 'distributors_payment_methods', :class_name => 'Enterprise', association_foreign_key: 'distributor_id'
 
   attr_accessible :distributor_ids