diff --git a/Library/Homebrew/cmd/postinstall.rb b/Library/Homebrew/cmd/postinstall.rb
index 02fd8a5f64..77320c2042 100644
--- a/Library/Homebrew/cmd/postinstall.rb
+++ b/Library/Homebrew/cmd/postinstall.rb
@@ -2,6 +2,7 @@
 #:    Rerun the post-install steps for <formula>.
 
 require "sandbox"
+require "formula_installer"
 
 module Homebrew
   module_function
@@ -9,43 +10,8 @@ module Homebrew
   def postinstall
     ARGV.resolved_formulae.each do |f|
       ohai "Postinstalling #{f}"
-      run_post_install(f)
-    end
-  end
-
-  def run_post_install(formula)
-    args = %W[
-      nice #{RUBY_PATH}
-      -W0
-      -I #{HOMEBREW_LOAD_PATH}
-      --
-      #{HOMEBREW_LIBRARY_PATH}/postinstall.rb
-      #{formula.path}
-    ].concat(ARGV.options_only)
-
-    if formula.head?
-      args << "--HEAD"
-    elsif formula.devel?
-      args << "--devel"
-    end
-
-    Utils.safe_fork do
-      if Sandbox.formula?(formula)
-        sandbox = Sandbox.new
-        formula.logs.mkpath
-        sandbox.record_log(formula.logs/"postinstall.sandbox.log")
-        sandbox.allow_write_temp_and_cache
-        sandbox.allow_write_log(formula)
-        sandbox.allow_write_xcode
-        sandbox.deny_write_homebrew_repository
-        sandbox.allow_write_cellar(formula)
-        Keg::TOP_LEVEL_DIRECTORIES.each do |dir|
-          sandbox.allow_write_path "#{HOMEBREW_PREFIX}/#{dir}"
-        end
-        sandbox.exec(*args)
-      else
-        exec(*args)
-      end
+      fi = FormulaInstaller.new(f)
+      fi.post_install
     end
   end
 end
diff --git a/Library/Homebrew/formula_installer.rb b/Library/Homebrew/formula_installer.rb
index 7ed473ee89..c4ac366118 100644
--- a/Library/Homebrew/formula_installer.rb
+++ b/Library/Homebrew/formula_installer.rb
@@ -7,7 +7,6 @@ require "caveats"
 require "cleaner"
 require "formula_cellar_checks"
 require "install_renamed"
-require "cmd/postinstall"
 require "debrew"
 require "sandbox"
 require "emoji"
@@ -837,7 +836,39 @@ class FormulaInstaller
   end
 
   def post_install
-    Homebrew.run_post_install(formula)
+    args = %W[
+      nice #{RUBY_PATH}
+      -W0
+      -I #{HOMEBREW_LOAD_PATH}
+      --
+      #{HOMEBREW_LIBRARY_PATH}/postinstall.rb
+      #{formula.path}
+    ].concat(ARGV.options_only)
+
+    if formula.head?
+      args << "--HEAD"
+    elsif formula.devel?
+      args << "--devel"
+    end
+
+    Utils.safe_fork do
+      if Sandbox.formula?(formula)
+        sandbox = Sandbox.new
+        formula.logs.mkpath
+        sandbox.record_log(formula.logs/"postinstall.sandbox.log")
+        sandbox.allow_write_temp_and_cache
+        sandbox.allow_write_log(formula)
+        sandbox.allow_write_xcode
+        sandbox.deny_write_homebrew_repository
+        sandbox.allow_write_cellar(formula)
+        Keg::TOP_LEVEL_DIRECTORIES.each do |dir|
+          sandbox.allow_write_path "#{HOMEBREW_PREFIX}/#{dir}"
+        end
+        sandbox.exec(*args)
+      else
+        exec(*args)
+      end
+    end
   rescue Exception => e # rubocop:disable Lint/RescueException
     opoo "The post-install step did not complete successfully"
     puts "You can try again using `brew postinstall #{formula.full_name}`"