diff --git a/fs/ext4/block_validity.c b/fs/ext4/block_validity.c
index dc79b75..4df8621 100644
--- a/fs/ext4/block_validity.c
+++ b/fs/ext4/block_validity.c
@@ -228,6 +228,7 @@
 	struct rb_node *n = sbi->system_blks.rb_node;
 
 	if ((start_blk <= le32_to_cpu(sbi->s_es->s_first_data_block)) ||
+	    (start_blk + count < start_blk) ||
 	    (start_blk + count > ext4_blocks_count(sbi->s_es)))
 		return 0;
 	while (n) {