diff --git a/lib/intercom/lib/flat_store.rb b/lib/intercom/lib/flat_store.rb
index 6971ca75..2077a2bd 100644
--- a/lib/intercom/lib/flat_store.rb
+++ b/lib/intercom/lib/flat_store.rb
@@ -2,7 +2,7 @@ module Intercom
   module Lib
 
     # Sub-class of {Hash} for storing custom data attributes.
-    # Doesn't allow nested Hashes or Arrays. And requires {String} or {Symbol} keys.
+    # Doesn't allow Arrays. And requires {String} or {Symbol} keys.
     class FlatStore < Hash
 
       def initialize(attributes={})
@@ -21,9 +21,16 @@ def [](key)
         super(key.to_s)
       end
 
+      def to_submittable_hash
+        # Filter out Custom Object references when submitting to API
+        self.reject do |key, value|
+          value.is_a?(Hash)
+        end
+      end
+
       private
       def validate_key_and_value(key, value)
-        raise ArgumentError.new("This does not support nested data structures (key: #{key}, value: #{value}") if value.is_a?(Array) || value.is_a?(Hash)
+        raise ArgumentError.new("This does not support nested data structures (key: #{key}, value: #{value}") if value.is_a?(Array)
         raise ArgumentError.new("Key must be String or Symbol: #{key}") unless key.is_a?(String) || key.is_a?(Symbol)
       end
     end
diff --git a/spec/unit/intercom/contact_spec.rb b/spec/unit/intercom/contact_spec.rb
index a8ffd978..6361905d 100644
--- a/spec/unit/intercom/contact_spec.rb
+++ b/spec/unit/intercom/contact_spec.rb
@@ -90,12 +90,10 @@
     _(contact.to_hash['custom_attributes']).must_equal 'mad' => 123, 'other' => now.to_i, 'thing' => 'yay'
   end
 
-  it 'rejects nested data structures in custom_attributes' do
+  it 'rejects lists in custom_attributes' do
     contact = Intercom::Contact.new
 
     _(proc { contact.custom_attributes['thing'] = [1] }).must_raise(ArgumentError)
-    _(proc { contact.custom_attributes['thing'] = { 1 => 2 } }).must_raise(ArgumentError)
-    _(proc { contact.custom_attributes['thing'] = { 1 => { 2 => 3 } } }).must_raise(ArgumentError)
 
     contact = Intercom::Contact.new(test_contact)
     _(proc { contact.custom_attributes['thing'] = [1] }).must_raise(ArgumentError)
diff --git a/spec/unit/intercom/lib/flat_store_spec.rb b/spec/unit/intercom/lib/flat_store_spec.rb
index 3188b579..412ed717 100644
--- a/spec/unit/intercom/lib/flat_store_spec.rb
+++ b/spec/unit/intercom/lib/flat_store_spec.rb
@@ -3,11 +3,15 @@
 require 'spec_helper'
 
 describe Intercom::Lib::FlatStore do
-  it 'raises if you try to set or merge in nested hash structures' do
+  it 'raises if you try to set arrays but allows hashes' do
     data = Intercom::Lib::FlatStore.new
     _(proc { data['thing'] = [1] }).must_raise ArgumentError
-    _(proc { data['thing'] = { 1 => 2 } }).must_raise ArgumentError
-    _(proc { Intercom::Lib::FlatStore.new(1 => { 2 => 3 }) }).must_raise ArgumentError
+  
+    data['thing'] = { 'key' => 'value' }
+    _(data['thing']).must_equal({ 'key' => 'value' })
+    
+    flat_store = Intercom::Lib::FlatStore.new('custom_object' => { 'type' => 'Order.list', 'instances' => [{'id' => '123'}] })
+    _(flat_store['custom_object']).must_equal({ 'type' => 'Order.list', 'instances' => [{'id' => '123'}] })
   end
 
   it 'raises if you try to use a non string key' do
@@ -28,4 +32,30 @@
     _(data['b']).must_equal 2
     _(data[:b]).must_equal 2
   end
+
+  describe '#to_submittable_hash' do
+    it 'filters out all hash values' do
+      data = Intercom::Lib::FlatStore.new(
+        'regular_attr' => 'value',
+        'number_attr' => 42,
+        'custom_object' => {
+          'type' => 'Order.list',
+          'instances' => [
+            { 'id' => '31', 'external_id' => 'ext_123' }
+          ]
+        },
+        'regular_hash' => { 'key' => 'value' },
+        'metadata' => { 'source' => 'api', 'version' => 2 }
+      )
+      
+      submittable = data.to_submittable_hash
+      
+      _(submittable['regular_attr']).must_equal 'value'
+      _(submittable['number_attr']).must_equal 42
+      
+      _(submittable.key?('custom_object')).must_equal false
+      _(submittable.key?('regular_hash')).must_equal false
+      _(submittable.key?('metadata')).must_equal false
+    end
+  end
 end
diff --git a/spec/unit/intercom/user_spec.rb b/spec/unit/intercom/user_spec.rb
index fa6deddb..a570abfe 100644
--- a/spec/unit/intercom/user_spec.rb
+++ b/spec/unit/intercom/user_spec.rb
@@ -106,12 +106,10 @@
     _(user.to_hash['companies']).must_equal companies
   end
 
-  it 'rejects nested data structures in custom_attributes' do
+  it 'rejects lists in custom_attributes' do
     user = Intercom::User.new
 
     _(proc { user.custom_attributes['thing'] = [1] }).must_raise(ArgumentError)
-    _(proc { user.custom_attributes['thing'] = { 1 => 2 } }).must_raise(ArgumentError)
-    _(proc { user.custom_attributes['thing'] = { 1 => { 2 => 3 } } }).must_raise(ArgumentError)
 
     user = Intercom::User.from_api(test_user)
     _(proc { user.custom_attributes['thing'] = [1] }).must_raise(ArgumentError)