diff --git a/usr/mallocator/main.c b/usr/mallocator/main.c
index 7be0a6a..24961f4 100644
--- a/usr/mallocator/main.c
+++ b/usr/mallocator/main.c
@@ -20,7 +20,8 @@
 #include <aos/deferred.h>
 
 #define NUM_SMALL_BUFFERS 128
-#define NUM_THREADS 512
+// one thread is for the main and MAX_THREADS is 256
+#define NUM_THREADS (256 - 1)
 
 static struct thread* threads[NUM_THREADS];