diff --git a/test/-ext-/thread_fd_close/test_thread_fd_close.rb b/test/-ext-/thread_fd_close/test_thread_fd_close.rb
index e6c3895da7..90993cf63d 100644
--- a/test/-ext-/thread_fd_close/test_thread_fd_close.rb
+++ b/test/-ext-/thread_fd_close/test_thread_fd_close.rb
@@ -6,6 +6,8 @@ require 'io/wait'
 class TestThreadFdClose < Test::Unit::TestCase
 
   def test_thread_fd_close
+    skip "MJIT thread is unexpected for this" if RubyVM::MJIT.enabled?
+
     IO.pipe do |r, w|
       th = Thread.new do
         begin
diff --git a/test/rubygems/test_gem_util.rb b/test/rubygems/test_gem_util.rb
index d17fc77fd9..205cd89611 100644
--- a/test/rubygems/test_gem_util.rb
+++ b/test/rubygems/test_gem_util.rb
@@ -5,6 +5,7 @@ require 'rubygems/util'
 class TestGemUtil < Gem::TestCase
 
   def test_class_popen
+    skip "MJIT executes process and it's caught by Process.wait(-1)" if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled?
     assert_equal "0\n", Gem::Util.popen(Gem.ruby, '-e', 'p 0')
 
     assert_raises Errno::ECHILD do