diff --git a/fmrest-spyke.gemspec b/fmrest-spyke.gemspec
index 8c0606b..388c210 100644
--- a/fmrest-spyke.gemspec
+++ b/fmrest-spyke.gemspec
@@ -22,6 +22,7 @@ Gem::Specification.new do |spec|
 
   spec.add_dependency "fmrest-core", "=#{FmRest::VERSION}"
   spec.add_dependency "spyke", ">= 7.0"
+  spec.add_dependency "activesupport", ">= 5.2"
 
   # NOTE: Add development deps to fmrest.gemspec
 end
diff --git a/lib/fmrest/spyke/model/associations.rb b/lib/fmrest/spyke/model/associations.rb
index d84e9a8..b65955c 100644
--- a/lib/fmrest/spyke/model/associations.rb
+++ b/lib/fmrest/spyke/model/associations.rb
@@ -16,12 +16,8 @@ module Associations
           # to parse the portalData JSON in SpykeFormatter
           #
           # TODO: Replace this with options in PortalBuilder
-          class_attribute :portal_options, instance_accessor: false, instance_predicate: false
-
-          # class_attribute supports a :default option since ActiveSupport 5.2,
-          # but we want to support previous versions too so we set the default
-          # manually instead
-          self.portal_options = {}.freeze
+          class_attribute :portal_options, instance_accessor: false, instance_predicate: false,
+            default: {}.freeze
 
           class << self; private :portal_options=; end
 
diff --git a/lib/fmrest/spyke/model/attributes.rb b/lib/fmrest/spyke/model/attributes.rb
index 35822be..5c25220 100644
--- a/lib/fmrest/spyke/model/attributes.rb
+++ b/lib/fmrest/spyke/model/attributes.rb
@@ -32,12 +32,8 @@ module Attributes
 
           # Keep track of attribute mappings so we can get the FM field names
           # for changed attributes
-          class_attribute :mapped_attributes, instance_writer: false, instance_predicate: false
-
-          # class_attribute supports a :default option since ActiveSupport 5.2,
-          # but we want to support previous versions too so we set the default
-          # manually instead
-          self.mapped_attributes = ::ActiveSupport::HashWithIndifferentAccess.new.freeze
+          class_attribute :mapped_attributes, instance_writer: false, instance_predicate: false,
+            default: ::ActiveSupport::HashWithIndifferentAccess.new.freeze
 
           class << self; private :mapped_attributes=; end