diff --git a/Library/Homebrew/cmd/update-report.rb b/Library/Homebrew/cmd/update-report.rb
index c5ed558914..b1fa02ddbe 100644
--- a/Library/Homebrew/cmd/update-report.rb
+++ b/Library/Homebrew/cmd/update-report.rb
@@ -192,25 +192,41 @@ module Homebrew
   def migrate_cache_entries_to_double_dashes(initial_version)
     return if initial_version > "1.7.1"
 
-    HOMEBREW_CACHE.children.each do |child|
-      next unless child.file?
+    Formula.each do |formula|
+      specs = [*formula.stable, *formula.devel, *formula.head]
 
-      next unless /^(?<prefix>[^\.]+[^\-])\-(?<suffix>[^\-].*)/ =~ child.basename.to_s
-      target = HOMEBREW_CACHE/"#{prefix}--#{suffix}"
+      resources = [*formula.bottle&.resource] + specs.flat_map do |spec|
+        [
+          spec,
+          *spec.resources.values,
+          *spec.patches.select(&:external?).map(&:resource),
+        ]
+      end
 
-      next if suffix.include?("--") && !suffix.start_with?("patch")
+      resources.each do |resource|
+        downloader = resource.downloader
 
-      if target.exist?
-        begin
-          FileUtils.rm_rf child
-        rescue Errno::EACCES
-          opoo "Could not remove #{child}, please do so manually."
-        end
-      else
-        begin
-          FileUtils.mv child, target
-        rescue Errno::EACCES
-          opoo "Could not move #{child} to #{target}, please do so manually."
+        name = resource.download_name
+        version = resource.version
+
+        new_location = downloader.cached_location
+        extname = new_location.extname
+        old_location = downloader.cached_location.dirname/"#{name}-#{version}#{extname}"
+
+        next unless old_location.file?
+
+        if new_location.exist?
+          begin
+            FileUtils.rm_rf old_location
+          rescue Errno::EACCES
+            opoo "Could not remove #{old_location}, please do so manually."
+          end
+        else
+          begin
+            FileUtils.mv old_location, new_location
+          rescue Errno::EACCES
+            opoo "Could not move #{old_location} to #{new_location}, please do so manually."
+          end
         end
       end
     end
diff --git a/Library/Homebrew/software_spec.rb b/Library/Homebrew/software_spec.rb
index d0a104bb7a..b41b069cdb 100644
--- a/Library/Homebrew/software_spec.rb
+++ b/Library/Homebrew/software_spec.rb
@@ -25,7 +25,7 @@ class SoftwareSpec
   attr_reader :compiler_failures
 
   def_delegators :@resource, :stage, :fetch, :verify_download_integrity, :source_modified_time
-  def_delegators :@resource, :cached_download, :clear_cache
+  def_delegators :@resource, :download_name, :cached_download, :clear_cache
   def_delegators :@resource, :checksum, :mirrors, :specs, :using
   def_delegators :@resource, :version, :mirror, *Checksum::TYPES
   def_delegators :@resource, :downloader
diff --git a/Library/Homebrew/test/cmd/update-report_spec.rb b/Library/Homebrew/test/cmd/update-report_spec.rb
index e4cfceeb17..a796d392f1 100644
--- a/Library/Homebrew/test/cmd/update-report_spec.rb
+++ b/Library/Homebrew/test/cmd/update-report_spec.rb
@@ -2,51 +2,45 @@ require "cmd/update-report"
 
 describe "brew update-report" do
   describe "::migrate_cache_entries_to_double_dashes" do
-    let(:legacy_cache_file) { HOMEBREW_CACHE/"foo-1.2.3.tar.gz" }
-    let(:renamed_cache_file) { HOMEBREW_CACHE/"foo--1.2.3.tar.gz" }
+    let(:formula_name) { "foo" }
+    let(:f) {
+      formula formula_name do
+        url "https://example.com/foo-1.2.3.tar.gz"
+        version "1.2.3"
+      end
+    }
+    let(:old_cache_file) { HOMEBREW_CACHE/"#{formula_name}-1.2.3.tar.gz" }
+    let(:new_cache_file) { HOMEBREW_CACHE/"#{formula_name}--1.2.3.tar.gz" }
 
     before(:each) do
-      FileUtils.touch legacy_cache_file
+      FileUtils.touch old_cache_file
+      allow(Formula).to receive(:each).and_yield(f)
     end
 
     it "moves old files to use double dashes when upgrading from <= 1.7.1" do
       Homebrew.migrate_cache_entries_to_double_dashes(Version.new("1.7.1"))
 
-      expect(legacy_cache_file).not_to exist
-      expect(renamed_cache_file).to exist
+      expect(old_cache_file).not_to exist
+      expect(new_cache_file).to exist
     end
 
     context "when the formula name contains dashes" do
-      let(:legacy_cache_file) { HOMEBREW_CACHE/"foo-bar-1.2.3.tar.gz" }
-      let(:renamed_cache_file) { HOMEBREW_CACHE/"foo-bar--1.2.3.tar.gz" }
+      let(:formula_name) { "foo-bar" }
 
       it "does not introduce extra double dashes when called multiple times" do
         Homebrew.migrate_cache_entries_to_double_dashes(Version.new("1.7.1"))
         Homebrew.migrate_cache_entries_to_double_dashes(Version.new("1.7.1"))
 
-        expect(legacy_cache_file).not_to exist
-        expect(renamed_cache_file).to exist
-      end
-    end
-
-    context "when the file is a patch and the formula name contains dashes" do
-      let(:legacy_cache_file) { HOMEBREW_CACHE/"foo-bar-patch--1.2.3.tar.gz" }
-      let(:renamed_cache_file) { HOMEBREW_CACHE/"foo-bar--patch--1.2.3.tar.gz" }
-
-      it "does not introduce extra double dashes when called multiple times" do
-        Homebrew.migrate_cache_entries_to_double_dashes(Version.new("1.7.1"))
-        Homebrew.migrate_cache_entries_to_double_dashes(Version.new("1.7.1"))
-
-        expect(legacy_cache_file).not_to exist
-        expect(renamed_cache_file).to exist
+        expect(old_cache_file).not_to exist
+        expect(new_cache_file).to exist
       end
     end
 
     it "does not move files if upgrading from > 1.7.1" do
       Homebrew.migrate_cache_entries_to_double_dashes(Version.new("1.7.2"))
 
-      expect(legacy_cache_file).to exist
-      expect(renamed_cache_file).not_to exist
+      expect(old_cache_file).to exist
+      expect(new_cache_file).not_to exist
     end
   end
 end