diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 0ad99ac..c716ab8 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -23,5 +23,8 @@ jobs:
         ruby-version: ${{ matrix.ruby }}
         rubygems: ${{ matrix.ruby < '2.7' && '3.4.22' || '' }}
         bundler-cache: true
+    - name: Add RUBYLIB to load fake etc.rb
+      run:
+        echo RUBYLIB=%CD:\=/%/lib >> $GITHUB_ENV
     - name: Run test
       run: bundle exec rake compile test
diff --git a/Rakefile b/Rakefile
index 18a7e4e..bead40b 100644
--- a/Rakefile
+++ b/Rakefile
@@ -1,6 +1,7 @@
 require "bundler/gem_tasks"
 require "rake/testtask"
 require "rdoc/task"
+require "etc"
 
 name = "etc"
 
diff --git a/lib/etc.rb b/lib/etc.rb
new file mode 100644
index 0000000..74d81f9
--- /dev/null
+++ b/lib/etc.rb
@@ -0,0 +1,9 @@
+dir = __dir__
+$:.delete(dir)
+if libs = ENV.delete("RUBYLIB")
+  libs = libs.split(File::PATH_SEPARATOR).select do |d|
+    !File.identical?(d, dir)
+  end
+  ENV["RUBYLIB"] = libs.join(File::PATH_SEPARATOR) unless libs.empty?
+end
+raise LoadError, "etc"