diff --git a/Library/Homebrew/keg_relocate.rb b/Library/Homebrew/keg_relocate.rb
index 4d30c4c149..759f526ff6 100644
--- a/Library/Homebrew/keg_relocate.rb
+++ b/Library/Homebrew/keg_relocate.rb
@@ -34,7 +34,7 @@ class Keg
     end
 
     def start_with_old_value?(key, text)
-      text.match?(/^#{@replacement_map.fetch(key)}/)
+      text.match?(/^#{@replacement_map.fetch(key).first}/)
     end
 
     sig { params(text: String).void }
diff --git a/Library/Homebrew/test/keg_relocate/relocation_spec.rb b/Library/Homebrew/test/keg_relocate/relocation_spec.rb
index ff0838c907..503aa3dd14 100644
--- a/Library/Homebrew/test/keg_relocate/relocation_spec.rb
+++ b/Library/Homebrew/test/keg_relocate/relocation_spec.rb
@@ -59,6 +59,17 @@ describe Keg::Relocation do
     REPLACED
   end
 
+  specify "#start_with_old_value?" do
+    relocation = setup_relocation
+
+    expect(relocation.start_with_old_value?(:prefix, "#{HOMEBREW_PREFIX}/foo")).to be true
+    expect(relocation.start_with_old_value?(:prefix, "foo#{HOMEBREW_PREFIX}/bar")).to be false
+    expect(relocation.start_with_old_value?(:cellar, "#{HOMEBREW_CELLAR}/foo")).to be true
+    expect(relocation.start_with_old_value?(:cellar, "foo#{HOMEBREW_CELLAR}/bar")).to be false
+    expect(relocation.start_with_old_value?(:repository_placeholder, "@@HOMEBREW_REPOSITORY@@/foo")).to be true
+    expect(relocation.start_with_old_value?(:library_placeholder, "foo@@HOMEBREW_LIBRARY@@/bar")).to be false
+  end
+
   specify "::path_regex" do
     expect(described_class.path_regex(prefix)).to eq escaped_prefix
     expect(described_class.path_regex("foo.bar")).to eq(/(?<![a-zA-Z0-9])foo\.bar/)