diff --git a/app/controllers/file_controller.rb b/app/controllers/file_controller.rb
index f41392db..d8130c4d 100644
--- a/app/controllers/file_controller.rb
+++ b/app/controllers/file_controller.rb
@@ -70,7 +70,7 @@ def cache_headers
   end
 
   def current_file
-    @file ||= StacksFile.new(id: params[:id], file_name: params[:file_name], cocina:)
+    @file ||= StacksFile.new(file_name: params[:file_name], cocina:)
   end
 
   def cocina
diff --git a/app/controllers/iiif/auth/v2/probe_service_controller.rb b/app/controllers/iiif/auth/v2/probe_service_controller.rb
index 719d070c..551b659a 100644
--- a/app/controllers/iiif/auth/v2/probe_service_controller.rb
+++ b/app/controllers/iiif/auth/v2/probe_service_controller.rb
@@ -13,9 +13,12 @@ def show # rubocop:disable Metrics:AbcSize
           stacks_uri = params[:id] # this is a fully qualified URI to the resource on the stacks that the user is requesting access to
           parsed_uri = parse_uri(stacks_uri)
 
-          file = StacksFile.new(id: parsed_uri[:druid], file_name: parsed_uri[:file_name], cocina: Cocina.find(parsed_uri[:druid]))
-
           json = { '@context': 'http://iiif.io/api/auth/2/context.json', type: 'AuthProbeResult2' }
+          begin
+            file = StacksFile.new(file_name: parsed_uri[:file_name], cocina: Cocina.find(parsed_uri[:druid]))
+          rescue Purl::Exception
+            return render json: json.merge(status: 404, note: { en: ["Unable to find #{parsed_uri[:druid]}"] })
+          end
 
           if !file.valid?
             json[:status] = 400
diff --git a/app/controllers/iiif_controller.rb b/app/controllers/iiif_controller.rb
index f4b44503..89d3488f 100644
--- a/app/controllers/iiif_controller.rb
+++ b/app/controllers/iiif_controller.rb
@@ -153,7 +153,6 @@ def canonical_url
 
   def stacks_file
     StacksFile.new(
-      id: identifier_params[:id],
       file_name: "#{identifier_params[:file_name]}.jp2",
       cocina: Cocina.find(identifier_params[:id])
     )
diff --git a/app/controllers/legacy_image_service_controller.rb b/app/controllers/legacy_image_service_controller.rb
index 7dfea079..ced816f4 100644
--- a/app/controllers/legacy_image_service_controller.rb
+++ b/app/controllers/legacy_image_service_controller.rb
@@ -31,7 +31,7 @@ def load_image
   end
 
   def stacks_file
-    StacksFile.new(id:, file_name:, cocina: Cocina.find(id))
+    StacksFile.new(file_name:, cocina: Cocina.find(id))
   end
 
   def iiif_params
diff --git a/app/controllers/media_controller.rb b/app/controllers/media_controller.rb
index 5531aeac..2a2abb71 100644
--- a/app/controllers/media_controller.rb
+++ b/app/controllers/media_controller.rb
@@ -70,7 +70,7 @@ def load_media
   end
 
   def stacks_file
-    StacksFile.new(id: params[:id], file_name: params[:file_name], cocina: Cocina.find(params[:id]))
+    StacksFile.new(file_name: params[:file_name], cocina: Cocina.find(params[:id]))
   end
 
   def current_media
diff --git a/app/models/cocina.rb b/app/models/cocina.rb
index 92175ea6..6492748c 100644
--- a/app/models/cocina.rb
+++ b/app/models/cocina.rb
@@ -32,6 +32,10 @@ def initialize(data)
 
   attr_accessor :data
 
+  def druid
+    @druid ||= data.fetch('externalIdentifier').delete_prefix('druid:')
+  end
+
   def find_file(file_name)
     file_sets = data.dig('structural', 'contains')
     raise(ActionController::MissingFile, "File not found '#{file_name}'") unless file_sets # Trap for Collections
@@ -61,7 +65,7 @@ def files(&)
   def files_from_json
     data.dig('structural', 'contains').each do |fileset|
       fileset.dig('structural', 'contains').each do |file|
-        file = StacksFile.new(id: data.fetch('externalIdentifier').delete_prefix('druid:'), file_name: file['filename'], cocina: self)
+        file = StacksFile.new(file_name: file['filename'], cocina: self)
         yield file
       end
     end
diff --git a/app/models/stacks_file.rb b/app/models/stacks_file.rb
index 7911bd6b..76b2897f 100644
--- a/app/models/stacks_file.rb
+++ b/app/models/stacks_file.rb
@@ -6,13 +6,16 @@
 class StacksFile
   include ActiveModel::Validations
 
-  def initialize(id:, file_name:, cocina:)
-    @id = id
+  def initialize(file_name:, cocina:)
     @file_name = file_name
     @cocina = cocina
   end
 
-  attr_reader :id, :file_name, :cocina
+  attr_reader :file_name, :cocina
+
+  def id
+    cocina.druid
+  end
 
   validates :id, format: { with: StorageRoot::DRUID_PARTS_PATTERN }
 
@@ -42,7 +45,7 @@ def treeified_path
   end
 
   def storage_root
-    @storage_root ||= StorageRoot.new(druid: id, file_name:)
+    @storage_root ||= StorageRoot.new(cocina:, file_name:)
   end
 
   def stacks_rights
diff --git a/app/models/stacks_rights.rb b/app/models/stacks_rights.rb
index 26677464..df27ac94 100644
--- a/app/models/stacks_rights.rb
+++ b/app/models/stacks_rights.rb
@@ -5,6 +5,8 @@
 class StacksRights
   attr_reader :cocina_file, :cocina
 
+  # @param [String] file_name
+  # @param [Cocina] cocina
   def initialize(file_name:, cocina:)
     @cocina = cocina
     @cocina_file = cocina.find_file(file_name)
diff --git a/app/models/storage_root.rb b/app/models/storage_root.rb
index dc2965ad..6e4d6052 100644
--- a/app/models/storage_root.rb
+++ b/app/models/storage_root.rb
@@ -4,10 +4,17 @@
 class StorageRoot
   DRUID_PARTS_PATTERN = /\A([b-df-hjkmnp-tv-z]{2})([0-9]{3})([b-df-hjkmnp-tv-z]{2})([0-9]{4})\z/i
 
-  def initialize(druid:, file_name:)
-    @druid = druid
-    @druid_parts = druid.match(DRUID_PARTS_PATTERN)
+  # @param [String] file_name
+  # @param [Cocina] cocina
+  def initialize(file_name:, cocina:)
     @file_name = file_name
+    @cocina = cocina
+  end
+
+  delegate :druid, to: :cocina
+
+  def druid_parts
+    @druid_parts ||= druid.match(DRUID_PARTS_PATTERN)
   end
 
   def absolute_path
@@ -28,7 +35,7 @@ def treeified_id
 
   private
 
-  attr_reader :druid, :druid_parts, :file_name
+  attr_reader :cocina, :file_name
 
   def path_finder
     @path_finder ||= path_finder_class.new(treeified_id:, druid:, file_name:)
diff --git a/spec/abilities/cocina_ability_spec.rb b/spec/abilities/cocina_ability_spec.rb
index 8d166e30..2b36196e 100644
--- a/spec/abilities/cocina_ability_spec.rb
+++ b/spec/abilities/cocina_ability_spec.rb
@@ -15,6 +15,7 @@
 
   let(:public_json) do
     {
+      'externalIdentifier' => 'yx350pf4616',
       'structural' => {
         'contains' => [
           {
@@ -56,13 +57,13 @@
 
   let(:cocina) { Cocina.new(public_json) }
   let(:file) do
-    StacksFile.new(id: 'xxxxxxx', file_name: 'file.csv', cocina:)
+    StacksFile.new(file_name: 'file.csv', cocina:)
   end
   let(:image) do
-    StacksImage.new(stacks_file: StacksFile.new(id: 'yx350pf4616', file_name: 'image.jpg', cocina:))
+    StacksImage.new(stacks_file: StacksFile.new(file_name: 'image.jpg', cocina:))
   end
   let(:media) do
-    StacksMediaStream.new(stacks_file: StacksFile.new(id: 'xxxxxxx', file_name: 'movie.mp4', cocina:))
+    StacksMediaStream.new(stacks_file: StacksFile.new(file_name: 'movie.mp4', cocina:))
   end
 
   let(:thumbnail_transformation) { IIIF::Image::OptionDecoder.decode(region: 'full', size: '!400,400') }
diff --git a/spec/controllers/file_controller_spec.rb b/spec/controllers/file_controller_spec.rb
index 165dcd75..8dd1fa51 100644
--- a/spec/controllers/file_controller_spec.rb
+++ b/spec/controllers/file_controller_spec.rb
@@ -9,6 +9,7 @@
 
   let(:public_json) do
     {
+      'externalIdentifier' => druid,
       'structural' => {
         'contains' => [
           {
diff --git a/spec/models/iiif_image_spec.rb b/spec/models/iiif_image_spec.rb
index 736639f4..4da51ad8 100644
--- a/spec/models/iiif_image_spec.rb
+++ b/spec/models/iiif_image_spec.rb
@@ -7,7 +7,7 @@
   let(:druid) { 'nr349ct7889' }
   let(:file_name) { 'image.jp2' }
   let(:transformation) { IIIF::Image::Transformation.new(size: 'full', region: 'full') }
-  let(:stacks_file) { StacksFile.new(id: druid, file_name:, cocina: Cocina.new({})) }
+  let(:stacks_file) { StacksFile.new(file_name:, cocina: Cocina.new({ "externalIdentifier" => druid })) }
   let(:instance) { described_class.new(stacks_file:, base_uri:, transformation:) }
 
   describe "#remote_id" do
diff --git a/spec/models/projection_spec.rb b/spec/models/projection_spec.rb
index 32642eb7..01b3900b 100644
--- a/spec/models/projection_spec.rb
+++ b/spec/models/projection_spec.rb
@@ -99,10 +99,10 @@
   describe '#response' do
     let(:druid) { 'nr349ct7889' }
     let(:file_name) { 'image.jp2' }
-    let(:cocina) { Cocina.new({}) }
+    let(:cocina) { Cocina.new({ 'externalIdentifier' => druid }) }
 
     context 'for an image' do
-      let(:image) { StacksImage.new(stacks_file: StacksFile.new(id: druid, file_name:, cocina:)) }
+      let(:image) { StacksImage.new(stacks_file: StacksFile.new(file_name:, cocina:)) }
 
       subject(:projection) { described_class.new(image, transformation) }
 
@@ -130,7 +130,7 @@
     end
 
     context 'for a restricted image' do
-      let(:image) { RestrictedImage.new(stacks_file: StacksFile.new(id: druid, file_name:, cocina:)) }
+      let(:image) { RestrictedImage.new(stacks_file: StacksFile.new(file_name:, cocina:)) }
 
       subject(:projection) { described_class.new(image, transformation) }
 
diff --git a/spec/models/stacks_file_spec.rb b/spec/models/stacks_file_spec.rb
index 01ddee07..cca03399 100644
--- a/spec/models/stacks_file_spec.rb
+++ b/spec/models/stacks_file_spec.rb
@@ -5,9 +5,10 @@
 RSpec.describe StacksFile do
   let(:druid) { 'nr349ct7889' }
   let(:file_name) { 'image.jp2' }
-  let(:instance) { described_class.new(id: druid, file_name:, cocina: Cocina.new({})) }
+  let(:cocina) {  Cocina.new({ 'externalIdentifier' => druid }) }
+  let(:instance) { described_class.new(file_name:, cocina:) }
   let(:path) { storage_root.absolute_path }
-  let(:storage_root) { StorageRoot.new(druid:, file_name:) }
+  let(:storage_root) { StorageRoot.new(cocina:, file_name:) }
 
   describe '#path' do
     subject { instance.path }
diff --git a/spec/models/stacks_image_spec.rb b/spec/models/stacks_image_spec.rb
index c470f1f6..7e5365d9 100644
--- a/spec/models/stacks_image_spec.rb
+++ b/spec/models/stacks_image_spec.rb
@@ -12,7 +12,7 @@
 
   describe "#info_service" do
     subject { instance.send(:info_service) }
-    let(:stacks_file) { StacksFile.new(id: 'nr349ct7889', file_name: 'image.jp2', cocina: Cocina.new({})) }
+    let(:stacks_file) { StacksFile.new(file_name: 'image.jp2', cocina: Cocina.new({ 'externalIdentifier' => 'nr349ct7889' })) }
     let(:instance) { described_class.new(stacks_file:) }
 
     it { is_expected.to be_a IiifMetadataService }
diff --git a/spec/requests/file_auth_request_spec.rb b/spec/requests/file_auth_request_spec.rb
index f50af36c..c3ee7412 100644
--- a/spec/requests/file_auth_request_spec.rb
+++ b/spec/requests/file_auth_request_spec.rb
@@ -11,9 +11,9 @@
   let(:druid) { 'nr349ct7889' }
   let(:file_name) { 'image.jp2' }
   let(:path) { storage_root.absolute_path }
-  let(:storage_root) { StorageRoot.new(druid:, file_name:) }
+  let(:storage_root) { StorageRoot.new(cocina:, file_name:) }
   let(:perms) { nil }
-  let(:stacks_file) { StacksFile.new(id: druid, file_name:, cocina:) }
+  let(:stacks_file) { StacksFile.new(file_name:, cocina:) }
   let(:cocina) { Cocina.new(public_json) }
 
   before do
@@ -26,6 +26,7 @@
     context 'stanford only (no location qualifications)' do
       let(:public_json) do
         {
+          'externalIdentifier' => druid,
           'structural' => {
             'contains' => [
               {
@@ -69,6 +70,7 @@
       context 'not stanford qualified in any way' do
         let(:public_json) do
           {
+            'externalIdentifier' => druid,
             'structural' => {
               'contains' => [
                 {
diff --git a/spec/requests/file_spec.rb b/spec/requests/file_spec.rb
index 2c7f9086..4e1a3a3c 100644
--- a/spec/requests/file_spec.rb
+++ b/spec/requests/file_spec.rb
@@ -11,6 +11,7 @@
   let(:file_name) { 'image.jp2' }
   let(:public_json) do
     {
+      'externalIdentifier' => druid,
       'structural' => {
         'contains' => [
           {
@@ -44,6 +45,7 @@
     let(:file_name) { 'path/to/image.jp2' }
     let(:public_json) do
       {
+        'externalIdentifier' => druid,
         'structural' => {
           'contains' => [
             {
diff --git a/spec/requests/iiif/auth/v2/probe_service_spec.rb b/spec/requests/iiif/auth/v2/probe_service_spec.rb
index 47b516bd..87d6682c 100644
--- a/spec/requests/iiif/auth/v2/probe_service_spec.rb
+++ b/spec/requests/iiif/auth/v2/probe_service_spec.rb
@@ -7,7 +7,7 @@
   let(:file_name) { 'image.jp2' }
   let(:stacks_uri) { "https://stacks-uat.stanford.edu/file/druid:#{id}/#{URI.encode_uri_component(file_name)}" }
   let(:stacks_uri_param) { URI.encode_uri_component(stacks_uri) }
-  let(:public_json) { '{}' }
+  let(:public_json) { { "externalIdentifier" => "druid:nr349ct7889" } }
 
   # NOTE: For any unauthorized responses, the status from the service is OK...the access status of the resource is in the response body
 
@@ -46,14 +46,15 @@
     let(:id) { '111' }
 
     before do
+      allow(Cocina).to receive(:find).and_raise(Purl::Exception)
       get "/iiif/auth/v2/probe?id=#{stacks_uri_param}"
     end
 
     it 'returns a success response' do
       expect(response).to have_http_status :ok
       expect(response.parsed_body).to eq("@context" => "http://iiif.io/api/auth/2/context.json",
-                                         "note" => { "en" => ["Id is invalid"] },
-                                         "status" => 400,
+                                         "note" => { "en" => ["Unable to find 111"] },
+                                         "status" => 404,
                                          "type" => "AuthProbeResult2")
     end
   end
@@ -73,6 +74,7 @@
   context 'when the user has access to the resource because it is world accessible' do
     let(:public_json) do
       {
+        "externalIdentifier" => "druid:nr349ct7889",
         'structural' => {
           'contains' => [
             {
@@ -100,9 +102,6 @@
     context 'when druid has a prefix' do
       it 'returns a success response' do
         expect(response).to have_http_status :ok
-        # Ensure the druid doesn't have a prefix:
-        expect(StacksFile).to have_received(:new).with(hash_including(id: "nr349ct7889"))
-
         expect(response.parsed_body).to include({
                                                   "@context" => "http://iiif.io/api/auth/2/context.json",
                                                   "type" => "AuthProbeResult2",
@@ -116,9 +115,6 @@
 
       it 'returns a success response' do
         expect(response).to have_http_status :ok
-        # Ensure the druid doesn't have a prefix:
-        expect(StacksFile).to have_received(:new).with(hash_including(id: "nr349ct7889"))
-
         expect(response.parsed_body).to include({
                                                   "@context" => "http://iiif.io/api/auth/2/context.json",
                                                   "type" => "AuthProbeResult2",
@@ -145,6 +141,7 @@
     let(:file_name) { 'SC0193_1982-013_b06_f01_1981-09-29.mp4' }
     let(:public_json) do
       {
+        "externalIdentifier" => "druid:nr349ct7889",
         'structural' => {
           'contains' => [
             {
@@ -183,8 +180,6 @@
   end
 
   context 'when the requested file does not exist' do
-    let(:public_json) { {} }
-
     before do
       allow_any_instance_of(StacksFile).to receive(:readable?).and_return(nil)
       get "/iiif/auth/v2/probe?id=#{stacks_uri_param}"
@@ -203,6 +198,7 @@
   context 'when a Stanford only resource' do
     let(:public_json) do
       {
+        "externalIdentifier" => "druid:nr349ct7889",
         'structural' => {
           'contains' => [
             {
@@ -283,6 +279,7 @@
   context 'when the user does not have access to a location restricted resource' do
     let(:public_json) do
       {
+        "externalIdentifier" => "druid:nr349ct7889",
         'structural' => {
           'contains' => [
             {
@@ -346,6 +343,7 @@
   context 'when the user does not have access to a stanford restricted embargoed resource' do
     let(:public_json) do
       {
+        "externalIdentifier" => "druid:nr349ct7889",
         'access' => {
           'embargo' => {
             "releaseDate" => Time.parse('2099-05-15').getlocal.as_json
@@ -393,6 +391,7 @@
   context 'when the user does not have access to an embargoed resource' do
     let(:public_json) do
       {
+        "externalIdentifier" => "druid:nr349ct7889",
         'access' => {
           'embargo' => {
             "releaseDate" => Time.parse('2099-05-15').getlocal.as_json
diff --git a/spec/requests/iiif_auth_request_spec.rb b/spec/requests/iiif_auth_request_spec.rb
index 78deab19..cd01694d 100644
--- a/spec/requests/iiif_auth_request_spec.rb
+++ b/spec/requests/iiif_auth_request_spec.rb
@@ -19,7 +19,8 @@
   let(:transformation) { IIIF::Image::Transformation.new region:, size:, rotation:, quality:, format: }
   let(:druid) { 'nr349ct7889' }
   let(:file_name) { 'image.jp2' }
-  let(:stacks_file) { StacksFile.new(id: druid, file_name:, cocina: Cocina.new(public_json)) }
+  let(:cocina) { Cocina.new(public_json) }
+  let(:stacks_file) { StacksFile.new(file_name:, cocina:) }
   let(:current_image) { StacksImage.new(stacks_file:, transformation:) }
   let(:http_client) { instance_double(HTTP::Client) }
 
@@ -35,6 +36,7 @@
     context 'with a public item' do
       let(:public_json) do
         {
+          'externalIdentifier' => druid,
           'structural' => {
             'contains' => [
               {
@@ -69,6 +71,7 @@
     context 'with a stanford only item' do
       let(:public_json) do
         {
+          'externalIdentifier' => druid,
           'structural' => {
             'contains' => [
               {
@@ -121,6 +124,7 @@
     context 'with a location-restricted item' do
       let(:public_json) do
         {
+          'externalIdentifier' => druid,
           'structural' => {
             'contains' => [
               {
diff --git a/spec/requests/iiif_spec.rb b/spec/requests/iiif_spec.rb
index 30b43ff6..971803e0 100644
--- a/spec/requests/iiif_spec.rb
+++ b/spec/requests/iiif_spec.rb
@@ -16,6 +16,7 @@
 
   let(:public_json) do
     {
+      'externalIdentifier' => 'druid:nr349ct7889',
       'structural' => {
         'contains' => [
           {
@@ -71,6 +72,7 @@
     context 'for location-restricted documents' do
       let(:public_json) do
         {
+          'externalIdentifier' => 'druid:nr349ct7889',
           'structural' => {
             'contains' => [
               {
@@ -101,6 +103,7 @@
         context 'for a thumbnail' do
           let(:public_json) do
             {
+              'externalIdentifier' => 'druid:nr349ct7889',
               'structural' => {
                 'contains' => [
                   {
@@ -147,6 +150,7 @@
     context 'for stanford-restricted documents' do
       let(:public_json) do
         {
+          'externalIdentifier' => 'druid:nr349ct7889',
           'structural' => {
             'contains' => [
               {
@@ -187,6 +191,7 @@
     context 'where no one can download' do
       let(:public_json) do
         {
+          'externalIdentifier' => 'druid:nr349ct7889',
           'structural' => {
             'contains' => [
               {
@@ -223,6 +228,7 @@
     context 'where stanford only no download rights' do
       let(:public_json) do
         {
+          'externalIdentifier' => 'druid:nr349ct7889',
           'structural' => {
             'contains' => [
               {
diff --git a/spec/requests/media_auth_request_spec.rb b/spec/requests/media_auth_request_spec.rb
index 724bec57..7bf9e5b6 100644
--- a/spec/requests/media_auth_request_spec.rb
+++ b/spec/requests/media_auth_request_spec.rb
@@ -8,6 +8,7 @@
 
   let(:public_json) do
     {
+      'externalIdentifier' => druid,
       'structural' => {
         'contains' => [
           {
@@ -30,8 +31,7 @@
 
   let(:mock_media) do
     StacksMediaStream.new(
-      stacks_file: StacksFile.new(id: 'bb582xs1304',
-                                  file_name: 'file',
+      stacks_file: StacksFile.new(file_name: 'file',
                                   cocina:)
     )
   end
diff --git a/spec/requests/remote_iiif_image_delivery_spec.rb b/spec/requests/remote_iiif_image_delivery_spec.rb
index bbb5c0df..fff015ee 100644
--- a/spec/requests/remote_iiif_image_delivery_spec.rb
+++ b/spec/requests/remote_iiif_image_delivery_spec.rb
@@ -14,6 +14,7 @@
   end
   let(:public_json) do
     {
+      'externalIdentifier' => 'druid:nr349ct7889',
       'structural' => {
         'contains' => [
           {
diff --git a/spec/services/iiif_info_service_spec.rb b/spec/services/iiif_info_service_spec.rb
index e141be6b..c91783de 100644
--- a/spec/services/iiif_info_service_spec.rb
+++ b/spec/services/iiif_info_service_spec.rb
@@ -23,7 +23,7 @@
     let(:image) { StacksImage.new(stacks_file:) }
     let(:cocina) { Cocina.new(public_json) }
     let(:public_json) { {} }
-    let(:stacks_file) { StacksFile.new(id: 'nr349ct7889', file_name: 'nr349ct7889_00_0001', cocina:) }
+    let(:stacks_file) { StacksFile.new(file_name: 'nr349ct7889_00_0001', cocina:) }
     let(:source_info) { {} }
 
     before do
@@ -149,6 +149,7 @@
       let(:location_service) { image_info['service'] }
       let(:public_json) do
         {
+          'externalIdentifier' => 'nr349ct7889',
           'structural' => {
             'contains' => [
               {
diff --git a/spec/services/iiif_metadata_service_spec.rb b/spec/services/iiif_metadata_service_spec.rb
index f2c067b2..a8a1c655 100644
--- a/spec/services/iiif_metadata_service_spec.rb
+++ b/spec/services/iiif_metadata_service_spec.rb
@@ -6,7 +6,7 @@
   let(:base_uri) { 'https://sul-imageserver-uat.stanford.edu/cantaloupe/iiif/2/' } # 'image-server-path'
   let(:druid) { 'nr349ct7889' }
   let(:file_name) { 'image.jp2' }
-  let(:stacks_file) { StacksFile.new(id: druid, file_name:, cocina: Cocina.new({})) }
+  let(:stacks_file) { StacksFile.new(file_name:, cocina: Cocina.new({ 'externalIdentifier' => "druid:#{druid}" })) }
   let(:service) { described_class.new(stacks_file:, canonical_url: 'foo', base_uri:) }
   let(:http_client) { instance_double(HTTP::Client) }
 
diff --git a/spec/support/image_server_path.rb b/spec/support/image_server_path.rb
index 51d19be3..76ba1794 100644
--- a/spec/support/image_server_path.rb
+++ b/spec/support/image_server_path.rb
@@ -5,7 +5,8 @@
 # reading from OCFL or not
 module ImageServerPath
   def image_server_path(druid, file_name)
-    CGI.escape(StorageRoot.new(druid:, file_name:).relative_path)
+    cocina = instance_double(Cocina, druid:)
+    CGI.escape(StorageRoot.new(cocina:, file_name:).relative_path)
   end
 end