diff --git a/Library/Homebrew/cask/cask.rb b/Library/Homebrew/cask/cask.rb
index 8c0870c4ec..1b4a5309d0 100644
--- a/Library/Homebrew/cask/cask.rb
+++ b/Library/Homebrew/cask/cask.rb
@@ -275,6 +275,7 @@ module Cask
       @ruby_source_path = sourcefile_path.relative_path_from(tap.path)
     end
 
+    sig { returns(T::Hash[Symbol, String]) }
     def ruby_source_checksum
       @ruby_source_checksum ||= {
         sha256: Digest::SHA256.file(sourcefile_path).hexdigest,
@@ -300,7 +301,7 @@ module Cask
       # TODO: Clean this up when we deprecate the current JSON API and move to the internal JSON v3.
       ruby_source_sha256 = json_cask.dig(:ruby_source_checksum, :sha256)
       ruby_source_sha256 ||= json_cask[:ruby_source_sha256]
-      @ruby_source_checksum = { "sha256" => ruby_source_sha256 }
+      @ruby_source_checksum = { sha256: ruby_source_sha256 }
     end
 
     def to_s
diff --git a/Library/Homebrew/test/api/cask_spec.rb b/Library/Homebrew/test/api/cask_spec.rb
index 6758e1671c..a3d787993c 100644
--- a/Library/Homebrew/test/api/cask_spec.rb
+++ b/Library/Homebrew/test/api/cask_spec.rb
@@ -45,4 +45,30 @@ RSpec.describe Homebrew::API::Cask do
       expect(casks_output).to eq casks_hash
     end
   end
+
+  describe "::source_download", :needs_macos do
+    let(:cask) do
+      cask = Cask::CaskLoader::FromAPILoader.new(
+        "everything",
+        from_json: JSON.parse((TEST_FIXTURE_DIR/"cask/everything.json").read.strip),
+      ).load(config: nil)
+      cask
+    end
+
+    before do
+      allow_any_instance_of(Homebrew::API::Download).to receive(:fetch)
+      allow_any_instance_of(Homebrew::API::Download).to receive(:symlink_location).and_return(
+        TEST_FIXTURE_DIR/"cask/Casks/everything.rb",
+      )
+    end
+
+    it "specifies the correct URL and sha256" do
+      expect(Homebrew::API::Download).to receive(:new).with(
+        "https://raw.githubusercontent.com/Homebrew/homebrew-cask/abcdef1234567890abcdef1234567890abcdef12/Casks/everything.rb",
+        Checksum.new("d8d0d6b2e5ff65388eccb82236fd3aa157b4a29bb043a1f72b97f0e9b70e8320"),
+        any_args,
+      ).and_call_original
+      described_class.source_download(cask)
+    end
+  end
 end
diff --git a/Library/Homebrew/test/cask/cask_spec.rb b/Library/Homebrew/test/cask/cask_spec.rb
index fea5589a37..1cadf13a03 100644
--- a/Library/Homebrew/test/cask/cask_spec.rb
+++ b/Library/Homebrew/test/cask/cask_spec.rb
@@ -219,7 +219,11 @@ RSpec.describe Cask::Cask, :cask do
       it "returns expected hash" do
         allow(MacOS).to receive(:version).and_return(MacOSVersion.new("13"))
 
-        hash = Cask::CaskLoader.load("everything").to_h
+        cask = Cask::CaskLoader.load("everything")
+
+        expect(cask.tap).to receive(:git_head).and_return("abcdef1234567890abcdef1234567890abcdef12")
+
+        hash = cask.to_h
 
         expect(hash).to be_a(Hash)
         expect(JSON.pretty_generate(hash)).to eq(expected_json)
diff --git a/Library/Homebrew/test/support/fixtures/cask/everything.json b/Library/Homebrew/test/support/fixtures/cask/everything.json
index 59bebe0635..e17f57afed 100644
--- a/Library/Homebrew/test/support/fixtures/cask/everything.json
+++ b/Library/Homebrew/test/support/fixtures/cask/everything.json
@@ -96,7 +96,7 @@
   "disabled": false,
   "disable_date": null,
   "disable_reason": null,
-  "tap_git_head": null,
+  "tap_git_head": "abcdef1234567890abcdef1234567890abcdef12",
   "languages": [
     "en",
     "eo"