diff --git a/threading.c b/threading.c
index 85f56c3..fb0761f 100644
--- a/threading.c
+++ b/threading.c
@@ -384,7 +384,7 @@ void *thread_btm(){
 
 
 
-			char size_index[2] = { 0 };
+			signed char size_index[2] = { 0 };
 			if (total_dir_size > 1) {
 				size_index[0] = -1;
 				while (total_dir_size > 1 && size_index[0] < size_unit_count) {