diff --git a/easylogger/src/elog_async.c b/easylogger/src/elog_async.c
index a8b7e2f..95db74b 100755
--- a/easylogger/src/elog_async.c
+++ b/easylogger/src/elog_async.c
@@ -80,8 +80,10 @@ static pthread_t async_output_thread;
 
 /* Initialize OK flag */
 static bool init_ok = false;
+#ifdef ELOG_ASYNC_OUTPUT_USING_PTHREAD
 /* thread running flag */
 static bool thread_running = false;
+#endif
 /* asynchronous output mode enabled flag */
 static bool is_enabled = false;
 /* asynchronous output mode's ring buffer */