diff --git a/tool/lib/envutil.rb b/tool/lib/envutil.rb
index fedcf475279..5716bf72e9c 100644
--- a/tool/lib/envutil.rb
+++ b/tool/lib/envutil.rb
@@ -81,6 +81,11 @@ module EnvUtil
     self.timeout_scale = 10
   end
 
+  # Read here so that runners other than tool/lib/test/unit.rb, such as
+  # the test-unit gem in test-bundled-gems, also scale timeouts.
+  scale = (ENV["RUBY_TEST_TIMEOUT_SCALE"] || ENV["RUBY_TEST_SUBPROCESS_TIMEOUT_SCALE"]).to_f
+  self.timeout_scale = scale if scale > 0
+
   def apply_timeout_scale(t)
     if scale = EnvUtil.timeout_scale
       t * scale
diff --git a/tool/lib/test/unit.rb b/tool/lib/test/unit.rb
index 5ff4c66ff97..0dee35c47bc 100644
--- a/tool/lib/test/unit.rb
+++ b/tool/lib/test/unit.rb
@@ -1383,9 +1383,7 @@ module Test
       end
 
       def non_options(files, options)
-        if scale = options[:timeout_scale] or
-          (scale = ENV["RUBY_TEST_TIMEOUT_SCALE"] || ENV["RUBY_TEST_SUBPROCESS_TIMEOUT_SCALE"] and
-           (scale = scale.to_f) > 0)
+        if scale = options[:timeout_scale]
           EnvUtil.timeout_scale = scale
         end
         super
diff --git a/tool/test/test_envutil.rb b/tool/test/test_envutil.rb
index ae508948379..52cfd25dde3 100644
--- a/tool/test/test_envutil.rb
+++ b/tool/test/test_envutil.rb
@@ -17,6 +17,10 @@ class TestEnvUtil < Test::Unit::TestCase
     EnvUtil.timeout_scale = original_scale
   end
 
+  def test_timeout_scale_from_env
+    assert_separately([{"RUBY_TEST_TIMEOUT_SCALE" => "2.5"}], "assert_equal(2.5, EnvUtil.timeout_scale)")
+  end
+
   def test_invoke_ruby_captures_output_and_status
     stdout, stderr, status = EnvUtil.invoke_ruby(
       ["-e", "STDOUT.print('out'); STDERR.print('err')"],