diff --git a/Library/Homebrew/dev-cmd/bottle.rb b/Library/Homebrew/dev-cmd/bottle.rb
index 8386d76e3b..113c0bad39 100644
--- a/Library/Homebrew/dev-cmd/bottle.rb
+++ b/Library/Homebrew/dev-cmd/bottle.rb
@@ -480,7 +480,7 @@ module Homebrew
         update_or_add = nil
 
         Utils::Inreplace.inreplace(path) do |s|
-          if s.include? "bottle do"
+          if s.inreplace_string.include? "bottle do"
             update_or_add = "update"
             if args.keep_old?
               mismatches = []
diff --git a/Library/Homebrew/extend/string.rb b/Library/Homebrew/extend/string.rb
index 903168af60..90f3134f9d 100644
--- a/Library/Homebrew/extend/string.rb
+++ b/Library/Homebrew/extend/string.rb
@@ -3,22 +3,27 @@
 require "active_support/core_ext/object/blank"
 
 # Used by the inreplace function (in `utils.rb`).
-module StringInreplaceExtension
-  attr_accessor :errors
+class StringInreplaceExtension
+  attr_accessor :errors, :inreplace_string
+
+  def initialize(str)
+    @inreplace_string = str
+    @errors = []
+  end
 
   def self.extended(str)
     str.errors = []
   end
 
   def sub!(before, after)
-    result = super
+    result = inreplace_string.sub!(before, after)
     errors << "expected replacement of #{before.inspect} with #{after.inspect}" unless result
     result
   end
 
   # Warn if nothing was replaced
   def gsub!(before, after, audit_result = true)
-    result = super(before, after)
+    result = inreplace_string.gsub!(before, after)
     errors << "expected replacement of #{before.inspect} with #{after.inspect}" if audit_result && result.nil?
     result
   end
@@ -43,6 +48,6 @@ module StringInreplaceExtension
 
   # Finds the specified variable
   def get_make_var(flag)
-    self[/^#{Regexp.escape(flag)}[ \t]*[\\?+:!]?=[ \t]*((?:.*\\\n)*.*)$/, 1]
+    inreplace_string[/^#{Regexp.escape(flag)}[ \t]*[\\?+:!]?=[ \t]*((?:.*\\\n)*.*)$/, 1]
   end
 end
diff --git a/Library/Homebrew/sorbet/files.yaml b/Library/Homebrew/sorbet/files.yaml
index b3305ebf1f..6ce5e49baf 100644
--- a/Library/Homebrew/sorbet/files.yaml
+++ b/Library/Homebrew/sorbet/files.yaml
@@ -823,7 +823,6 @@ false:
   - ./test/version_spec.rb
   - ./unpack_strategy/uncompressed.rb
   - ./utils/gems.rb
-  - ./utils/inreplace.rb
   - ./version.rb
 
 true:
@@ -888,6 +887,7 @@ true:
   - ./test/support/helper/fixtures.rb
   - ./test/support/lib/config.rb
   - ./utils/bottles.rb
+  - ./utils/inreplace.rb
   - ./utils/link.rb
   - ./utils/notability.rb
   - ./utils/shebang.rb
diff --git a/Library/Homebrew/sorbet/rbi/utils/inreplace.rbi b/Library/Homebrew/sorbet/rbi/utils/inreplace.rbi
new file mode 100644
index 0000000000..6c9bfb5b3e
--- /dev/null
+++ b/Library/Homebrew/sorbet/rbi/utils/inreplace.rbi
@@ -0,0 +1,30 @@
+# typed: strict
+
+module Utils::Inreplace
+  include Kernel
+
+  sig { params(paths: T::Array[T.untyped], before: T.nilable(String), after: T.nilable(String), audit_result: T::Boolean).void }
+  def inreplace(paths, before = nil, after = nil, audit_result = true); end
+
+end
+
+class StringInreplaceExtension
+  sig { params(before: String, after: String).returns(T.nilable(String)) }
+  def sub!(before, after)
+  end
+
+  sig { params(before: T.nilable(String), after: T.nilable(String), audit_result: T::Boolean).returns(T.nilable(String)) }
+  def gsub!(before, after, audit_result = true); end
+
+  sig {params(flag: String, new_value: String).void}
+  def change_make_var!(flag, new_value)
+  end
+
+  sig {params(flags: T::Array[String]).void}
+  def remove_make_var!(flags)
+  end
+
+  sig {params(flag: String).returns(String)}
+  def get_make_var(flag)
+  end
+end
diff --git a/Library/Homebrew/test/inreplace_spec.rb b/Library/Homebrew/test/inreplace_spec.rb
index 965cd0035b..e35e5bd3ae 100644
--- a/Library/Homebrew/test/inreplace_spec.rb
+++ b/Library/Homebrew/test/inreplace_spec.rb
@@ -5,7 +5,7 @@ require "tempfile"
 require "utils/inreplace"
 
 describe StringInreplaceExtension do
-  subject { string.dup.extend(described_class) }
+  subject { described_class.new(string.dup) }
 
   describe "#change_make_var!" do
     context "flag" do
@@ -20,7 +20,7 @@ describe StringInreplaceExtension do
 
         it "is successfully replaced" do
           subject.change_make_var! "FLAG", "def"
-          expect(subject).to eq <<~EOS
+          expect(subject.inreplace_string).to eq <<~EOS
             OTHER=def
             FLAG=def
             FLAG2=abc
@@ -29,7 +29,7 @@ describe StringInreplaceExtension do
 
         it "is successfully appended" do
           subject.change_make_var! "FLAG", "\\1 def"
-          expect(subject).to eq <<~EOS
+          expect(subject.inreplace_string).to eq <<~EOS
             OTHER=def
             FLAG=abc def
             FLAG2=abc
@@ -47,7 +47,7 @@ describe StringInreplaceExtension do
 
         it "is successfully replaced" do
           subject.change_make_var! "CFLAGS", "-O3"
-          expect(subject).to eq <<~EOS
+          expect(subject.inreplace_string).to eq <<~EOS
             CFLAGS=-O3
             LDFLAGS\t=\t-lcrypto -lssl
           EOS
@@ -65,7 +65,7 @@ describe StringInreplaceExtension do
 
         it "is successfully replaced" do
           subject.change_make_var! "CFLAGS", "-O3"
-          expect(subject).to eq <<~EOS
+          expect(subject.inreplace_string).to eq <<~EOS
             CFLAGS=-O3
             LDFLAGS = -lcrypto -lssl
           EOS
@@ -84,7 +84,7 @@ describe StringInreplaceExtension do
 
       it "is successfully replaced" do
         subject.change_make_var! "FLAG", "def"
-        expect(subject).to eq <<~EOS
+        expect(subject.inreplace_string).to eq <<~EOS
           OTHER=def
           FLAG=def
           FLAG2=abc
@@ -102,7 +102,7 @@ describe StringInreplaceExtension do
 
       it "is successfully replaced" do
         subject.change_make_var! "FLAG", "def"
-        expect(subject).to eq <<~EOS
+        expect(subject.inreplace_string).to eq <<~EOS
           FLAG=def
           mv file_a file_b
         EOS
@@ -120,7 +120,7 @@ describe StringInreplaceExtension do
 
       it "is successfully replaced" do
         subject.change_make_var! "FLAG", "def"
-        expect(subject).to eq <<~EOS
+        expect(subject.inreplace_string).to eq <<~EOS
           OTHER=def
           FLAG=def
           FLAG2=abc
@@ -142,7 +142,7 @@ describe StringInreplaceExtension do
 
         it "is successfully removed" do
           subject.remove_make_var! "FLAG"
-          expect(subject).to eq <<~EOS
+          expect(subject.inreplace_string).to eq <<~EOS
             OTHER=def
             FLAG2 = def
           EOS
@@ -159,7 +159,7 @@ describe StringInreplaceExtension do
 
         it "is successfully removed" do
           subject.remove_make_var! "LDFLAGS"
-          expect(subject).to eq <<~EOS
+          expect(subject.inreplace_string).to eq <<~EOS
             CFLAGS\t=\t-Wall -O2
           EOS
         end
@@ -176,7 +176,7 @@ describe StringInreplaceExtension do
 
         it "is successfully removed" do
           subject.remove_make_var! "CFLAGS"
-          expect(subject).to eq <<~EOS
+          expect(subject.inreplace_string).to eq <<~EOS
             LDFLAGS = -lcrypto -lssl
           EOS
         end
@@ -195,7 +195,7 @@ describe StringInreplaceExtension do
 
       specify "are be successfully removed" do
         subject.remove_make_var! ["FLAG", "FLAG2"]
-        expect(subject).to eq <<~EOS
+        expect(subject.inreplace_string).to eq <<~EOS
           OTHER=def
           OTHER2=def
         EOS
@@ -250,7 +250,7 @@ describe StringInreplaceExtension do
 
     it "replaces the first occurrence" do
       subject.sub!("o", "e")
-      expect(subject).to eq("feo")
+      expect(subject.inreplace_string).to eq("feo")
     end
   end
 
@@ -259,7 +259,7 @@ describe StringInreplaceExtension do
 
     it "replaces all occurrences" do
       subject.gsub!("o", "e") # rubocop:disable Performance/StringReplacement
-      expect(subject).to eq("fee")
+      expect(subject.inreplace_string).to eq("fee")
     end
   end
 end
diff --git a/Library/Homebrew/test/string_spec.rb b/Library/Homebrew/test/string_spec.rb
index ed9cdc2deb..646d53765a 100644
--- a/Library/Homebrew/test/string_spec.rb
+++ b/Library/Homebrew/test/string_spec.rb
@@ -3,7 +3,7 @@
 require "extend/string"
 
 describe StringInreplaceExtension do
-  subject { string.extend(described_class) }
+  subject { described_class.new(string) }
 
   let(:string) { +"foobar" }
 
diff --git a/Library/Homebrew/utils/inreplace.rb b/Library/Homebrew/utils/inreplace.rb
index 59f2552679..bf0aeb7add 100644
--- a/Library/Homebrew/utils/inreplace.rb
+++ b/Library/Homebrew/utils/inreplace.rb
@@ -25,7 +25,8 @@ module Utils
       errors["`paths` (first) parameter"] = ["`paths` was empty"] if paths.blank?
 
       Array(paths).each do |path|
-        s = File.open(path, "rb", &:read).extend(StringInreplaceExtension)
+        str = File.open(path, "rb", &:read) || ""
+        s = StringInreplaceExtension.new(str)
 
         if before.nil? && after.nil?
           yield s
@@ -36,7 +37,7 @@ module Utils
 
         errors[path] = s.errors unless s.errors.empty?
 
-        Pathname(path).atomic_write(s)
+        Pathname(path).atomic_write(s.inreplace_string)
       end
 
       raise InreplaceError, errors unless errors.empty?