diff --git a/components/dfs/src/dfs_file.c b/components/dfs/src/dfs_file.c
index 15b42a2af9..4deba547be 100644
--- a/components/dfs/src/dfs_file.c
+++ b/components/dfs/src/dfs_file.c
@@ -516,7 +516,7 @@ void cat(const char* filename)
 	do
 	{
 		rt_memset(buffer, 0, sizeof(buffer));
-		length = dfs_file_read(&fd, buffer, 81);
+		length = dfs_file_read(&fd, buffer, sizeof(buffer)-1 );
 		if (length > 0)
 		{
 			rt_kprintf("%s", buffer);