diff --git a/test/ruby/test_backtrace.rb b/test/ruby/test_backtrace.rb
index c4545239a5..0c7677a781 100644
--- a/test/ruby/test_backtrace.rb
+++ b/test/ruby/test_backtrace.rb
@@ -212,6 +212,7 @@ class TestBacktrace < Test::Unit::TestCase
       assert_equal(bt, locs)
     ensure
       q << true
+      th.join
     end
   end
 
diff --git a/test/ruby/test_beginendblock.rb b/test/ruby/test_beginendblock.rb
index d9c1f56916..a4318493c1 100644
--- a/test/ruby/test_beginendblock.rb
+++ b/test/ruby/test_beginendblock.rb
@@ -127,6 +127,7 @@ EOW
 
   def test_endblock_raise
     ruby = EnvUtil.rubybin
+    th = nil
     out = IO.popen(
       [ruby,
        '-e', 'class C; def write(x); puts x; STDOUT.flush; sleep 0.01; end; end',
@@ -134,11 +135,13 @@ EOW
        '-e', 'END {raise "e1"}; END {puts "e2"}',
        '-e', 'END {raise "e3"}; END {puts "e4"}',
        '-e', 'END {raise "e5"}; END {puts "e6"}']) {|f|
-      Thread.new {sleep 5; Process.kill :KILL, f.pid}
+      th = Thread.new {sleep 5; Process.kill :KILL, f.pid}
       f.read
     }
     assert_match(/e1/, out)
     assert_match(/e6/, out)
+  ensure
+    th.kill if th.alive?
   end
 
   def test_nested_at_exit
diff --git a/test/ruby/test_proc.rb b/test/ruby/test_proc.rb
index 1c8a053cca..284b518121 100644
--- a/test/ruby/test_proc.rb
+++ b/test/ruby/test_proc.rb
@@ -407,6 +407,7 @@ class TestProc < Test::Unit::TestCase
     t = Thread.new { sleep }
     assert_raise(ThreadError) { t.instance_eval { initialize { } } }
     t.kill
+    t.join
   end
 
   def test_to_proc
diff --git a/test/ruby/test_threadgroup.rb b/test/ruby/test_threadgroup.rb
index e29c477247..f4c03de67e 100644
--- a/test/ruby/test_threadgroup.rb
+++ b/test/ruby/test_threadgroup.rb
@@ -5,10 +5,13 @@ require_relative 'envutil'
 class TestThreadGroup < Test::Unit::TestCase
   def test_thread_init
     thgrp = ThreadGroup.new
-    Thread.new{
+    th = Thread.new{
       thgrp.add(Thread.current)
-      assert_equal(thgrp, Thread.new{sleep 1}.group)
-    }.join
+      Thread.new{sleep 1}
+    }.value
+    assert_equal(thgrp, th.group)
+  ensure
+    th.join
   end
 
   def test_frozen_thgroup