diff --git a/Library/Homebrew/formula_pin.rb b/Library/Homebrew/formula_pin.rb
index 3682bcb3e4..141b30bad2 100644
--- a/Library/Homebrew/formula_pin.rb
+++ b/Library/Homebrew/formula_pin.rb
@@ -1,24 +1,28 @@
-# typed: true # rubocop:todo Sorbet/StrictSigil
+# typed: strict
 # frozen_string_literal: true
 
 require "keg"
 
 # Helper functions for pinning a formula.
 class FormulaPin
+  sig { params(formula: Formula).void }
   def initialize(formula)
     @formula = formula
   end
 
+  sig { returns(Pathname) }
   def path
     HOMEBREW_PINNED_KEGS/@formula.name
   end
 
+  sig { params(version: PkgVersion).void }
   def pin_at(version)
     HOMEBREW_PINNED_KEGS.mkpath
-    version_path = @formula.rack/version
+    version_path = @formula.rack/version.to_s
     path.make_relative_symlink(version_path) if !pinned? && version_path.exist?
   end
 
+  sig { void }
   def pin
     latest_keg = @formula.installed_kegs.max_by(&:scheme_and_version)
     return if latest_keg.nil?
@@ -26,19 +30,23 @@ class FormulaPin
     pin_at(latest_keg.version)
   end
 
+  sig { void }
   def unpin
     path.unlink if pinned?
     HOMEBREW_PINNED_KEGS.rmdir_if_possible
   end
 
+  sig { returns(T::Boolean) }
   def pinned?
     path.symlink?
   end
 
+  sig { returns(T::Boolean) }
   def pinnable?
     !@formula.installed_prefixes.empty?
   end
 
+  sig { returns(T.nilable(PkgVersion)) }
   def pinned_version
     Keg.new(path.resolved_path).version if pinned?
   end