diff --git a/lib/config/specification.yml b/lib/config/specification.yml
index aabf191..35e594f 100644
--- a/lib/config/specification.yml
+++ b/lib/config/specification.yml
@@ -730,6 +730,7 @@ expense_budgets:
     - description
     - expected_by
     - expense_ids
+    - external_reference_ids
     - fixed_fee
     - fixed_fee_item_ids
     - story_id
@@ -741,6 +742,7 @@ expense_budgets:
     - cost_per_unit_in_subunits
     - description
     - expected_by
+    - external_reference
     - fixed_fee
     - story_id
     - title
@@ -751,6 +753,7 @@ expense_budgets:
     - cost_per_unit_in_subunits
     - description
     - expected_by
+    - external_reference
     - fixed_fee
     - story_id
     - title
@@ -767,6 +770,9 @@ expense_budgets:
     story:
       foreign_key: story_id
       collection: stories
+    external_references:
+      foreign_key: external_reference_ids
+      collection: external_references
 
 expenses:
   validations:
diff --git a/spec/lib/mavenlink/expense_budget_spec.rb b/spec/lib/mavenlink/expense_budget_spec.rb
index e08b3df..4489faf 100644
--- a/spec/lib/mavenlink/expense_budget_spec.rb
+++ b/spec/lib/mavenlink/expense_budget_spec.rb
@@ -16,13 +16,14 @@
     it { is_expected.to respond_to :story_id }
     it { is_expected.to respond_to :title }
     it { is_expected.to respond_to :workspace_id }
+    it { is_expected.to respond_to :external_reference_ids }
   end
 
   describe ".create_attributes" do
     let(:subject) { described_class.create_attributes }
 
     it "includes expected attributes" do
-      is_expected.to match_array(%w[billable burns_budget cost_per_unit_in_subunits description expected_by fixed_fee story_id title workspace_id])
+      is_expected.to match_array(%w[billable burns_budget cost_per_unit_in_subunits description expected_by fixed_fee story_id title workspace_id external_reference])
     end
   end
 
@@ -30,7 +31,7 @@
     let(:subject) { described_class.update_attributes }
 
     it "includes expected attributes" do
-      is_expected.to match_array(%w[billable burns_budget cost_per_unit_in_subunits description expected_by fixed_fee story_id title])
+      is_expected.to match_array(%w[billable burns_budget cost_per_unit_in_subunits description expected_by fixed_fee story_id title external_reference])
     end
   end
 end