diff --git a/Library/Homebrew/extend/git_repository.rbi b/Library/Homebrew/extend/git_repository.rbi
index 534b936b96..9ffee241cf 100644
--- a/Library/Homebrew/extend/git_repository.rbi
+++ b/Library/Homebrew/extend/git_repository.rbi
@@ -1,8 +1,5 @@
 # typed: strict
 
 module GitRepositoryExtension
-  include Kernel
-
-  sig { params(args: T.any(String, Pathname)).returns(Pathname) }
-  def join(*args); end
+  requires_ancestor { Pathname }
 end
diff --git a/Library/Homebrew/extend/pathname.rbi b/Library/Homebrew/extend/pathname.rbi
index 12a94cd3eb..a682b461ee 100644
--- a/Library/Homebrew/extend/pathname.rbi
+++ b/Library/Homebrew/extend/pathname.rbi
@@ -1,19 +1,9 @@
 # typed: strict
 
 module DiskUsageExtension
-  include Kernel
-
-  def exist?; end
-
-  def symlink?; end
-
-  def resolved_path; end
+  requires_ancestor { Pathname }
 end
 
 module ObserverPathnameExtension
-  include Kernel
-
-  def dirname; end
-
-  def basename; end
+  requires_ancestor { Pathname }
 end
diff --git a/Library/Homebrew/os/mac/version.rb b/Library/Homebrew/os/mac/version.rb
index fd709f72f2..d407e882ac 100644
--- a/Library/Homebrew/os/mac/version.rb
+++ b/Library/Homebrew/os/mac/version.rb
@@ -45,7 +45,7 @@ module OS
       sig { returns(T.self_type) }
       def strip_patch
         # Big Sur is 11.x but Catalina is 10.15.x.
-        if major >= 11
+        if T.must(major) >= 11
           self.class.new(major.to_s)
         else
           major_minor
diff --git a/Library/Homebrew/os/mac/version.rbi b/Library/Homebrew/os/mac/version.rbi
deleted file mode 100644
index dc7c90848a..0000000000
--- a/Library/Homebrew/os/mac/version.rbi
+++ /dev/null
@@ -1,10 +0,0 @@
-# typed: strict
-
-module OS
-  module Mac
-    class Version
-      sig { returns(Token) }
-      def major; end
-    end
-  end
-end