diff --git a/spec/bundler/install/gemfile/git_spec.rb b/spec/bundler/install/gemfile/git_spec.rb
index 9130483aa1..24cf30eadb 100644
--- a/spec/bundler/install/gemfile/git_spec.rb
+++ b/spec/bundler/install/gemfile/git_spec.rb
@@ -1279,7 +1279,6 @@ RSpec.describe "bundle install with git sources" do
         s.extensions = ["ext/extconf.rb"]
         s.write "ext/extconf.rb", <<-RUBY
           require "mkmf"
-          $extout = "$(topdir)/" + RbConfig::CONFIG["EXTOUT"]
           create_makefile("foo")
         RUBY
         s.write "ext/foo.c", "void Init_foo() {}"
diff --git a/spec/bundler/install/gems/native_extensions_spec.rb b/spec/bundler/install/gems/native_extensions_spec.rb
index 51335272a9..907778a384 100644
--- a/spec/bundler/install/gems/native_extensions_spec.rb
+++ b/spec/bundler/install/gems/native_extensions_spec.rb
@@ -7,7 +7,6 @@ RSpec.describe "installing a gem with native extensions" do
         s.extensions = ["ext/extconf.rb"]
         s.write "ext/extconf.rb", <<-E
           require "mkmf"
-          $extout = "$(topdir)/" + RbConfig::CONFIG["EXTOUT"]
           name = "c_extension_bundle"
           dir_config(name)
           raise "OMG" unless with_config("c_extension") == "hello"
@@ -52,7 +51,6 @@ RSpec.describe "installing a gem with native extensions" do
       s.extensions = ["ext/extconf.rb"]
       s.write "ext/extconf.rb", <<-E
         require "mkmf"
-        $extout = "$(topdir)/" + RbConfig::CONFIG["EXTOUT"]
         name = "c_extension_bundle"
         dir_config(name)
         raise "OMG" unless with_config("c_extension") == "hello"
@@ -97,7 +95,6 @@ RSpec.describe "installing a gem with native extensions" do
           s.extensions = ["ext/extconf.rb"]
           s.write "ext/extconf.rb", <<-E
             require "mkmf"
-            $extout = "$(topdir)/" + RbConfig::CONFIG["EXTOUT"]
             name = "c_extension_bundle_#{n}"
             dir_config(name)
             raise "OMG" unless with_config("c_extension_#{n}") == "#{n}"
@@ -150,7 +147,6 @@ RSpec.describe "installing a gem with native extensions" do
       s.extensions = ["ext/extconf.rb"]
       s.write "ext/extconf.rb", <<-E
         require "mkmf"
-        $extout = "$(topdir)/" + RbConfig::CONFIG["EXTOUT"]
         name = "c_extension_bundle"
         dir_config(name)
         raise "OMG" unless with_config("c_extension") == "hello" && with_config("c_extension_bundle-dir") == "hola"
diff --git a/spec/bundler/support/builders.rb b/spec/bundler/support/builders.rb
index 68e3bd7c7b..8727b9a0b6 100644
--- a/spec/bundler/support/builders.rb
+++ b/spec/bundler/support/builders.rb
@@ -494,8 +494,6 @@ module Spec
         write "ext/extconf.rb", <<-RUBY
           require "mkmf"
 
-          $extout = "$(topdir)/" + RbConfig::CONFIG["EXTOUT"]
-
           extension_name = "#{name}_c"
           if extra_lib_dir = with_config("ext-lib")
             # add extra libpath if --with-ext-lib is