diff --git a/lib/droonga/http-benchmark.rb b/lib/droonga/http-benchmark.rb
index 0b9d4ba..b3d8b53 100644
--- a/lib/droonga/http-benchmark.rb
+++ b/lib/droonga/http-benchmark.rb
@@ -92,7 +92,7 @@ def process_requests
       end
 
       @client_threads.each do |client_thread|
-        client_thread.stop
+        client_thread.exit
       end
 
       @results = []