diff --git a/test/socket/test_tcp.rb b/test/socket/test_tcp.rb
index 8d55c011cf..a1657f027d 100644
--- a/test/socket/test_tcp.rb
+++ b/test/socket/test_tcp.rb
@@ -11,19 +11,13 @@ class TestTCPSocket < Test::Unit::TestCase
     svr = TCPServer.new("localhost", 0)
     Thread.new {
       c = svr.accept
-      Thread.pass until s
+      ObjectSpace.each_object(String) {|s|
+        s.replace "a" if s.length == 0x10000 and !s.frozen?
+      }
       c.print("x"*0x1000)
     }
     addr = svr.addr
     sock = TCPSocket.open(addr[2], addr[1])
-    Thread.new {
-      Thread.pass until c
-      Thread.critical = true
-      ObjectSpace.each_object(String) {|s|
-        s.replace "a" if s.length == 0x10000 and !s.frozen?
-      }
-      Thread.critical = false
-    }
     assert_raise(RuntimeError, SocketError) {
       sock.recvfrom(0x10000)
     }