diff --git a/fs/inode.c b/fs/inode.c
index 1ddaa2e..0b5c3fa 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -427,6 +427,7 @@ static void inode_lru_list_del(struct inode *inode)
 	if (!list_empty(&inode->i_lru)) {
 		list_del_init(&inode->i_lru);
 		inode->i_sb->s_nr_inodes_unused--;
+		BUG_ON(sb->s_nr_inodes_unused < 0);
 		this_cpu_dec(nr_unused);
 	}
 	spin_unlock(&inode->i_sb->s_inode_lru_lock);
@@ -739,6 +740,7 @@ long prune_icache_sb(struct super_block *sb, unsigned long nr_to_scan)
 			list_del_init(&inode->i_lru);
 			spin_unlock(&inode->i_lock);
 			sb->s_nr_inodes_unused--;
+			BUG_ON(sb->s_nr_inodes_unused < 0);
 			this_cpu_dec(nr_unused);
 			continue;
 		}
@@ -777,6 +779,7 @@ long prune_icache_sb(struct super_block *sb, unsigned long nr_to_scan)
 
 		list_move(&inode->i_lru, &freeable);
 		sb->s_nr_inodes_unused--;
+		BUG_ON(sb->s_nr_inodes_unused < 0);
 		this_cpu_dec(nr_unused);
 		freed++;
 	}