diff --git a/test/ruby/test_thread.rb b/test/ruby/test_thread.rb
index be8a28a..4ed25e5 100644
--- a/test/ruby/test_thread.rb
+++ b/test/ruby/test_thread.rb
@@ -104,7 +104,10 @@ class TestThread < Test::Unit::TestCase
         while i<max*max
           i+=1
           m.synchronize{
-            r += 1
+            t = r
+            t += 1
+            sleep 0.0001
+            r = t
           }
         end
       }