diff --git a/sbin/fsck_msdosfs/boot.c b/sbin/fsck_msdosfs/boot.c
index b1760c5c02df..667af93a86ea 100644
--- a/sbin/fsck_msdosfs/boot.c
+++ b/sbin/fsck_msdosfs/boot.c
@@ -221,7 +221,7 @@ readboot(int dosfs, struct bootblock *boot)
 		break;
 	}
 
-	if (boot->NumFatEntries < boot->NumClusters) {
+	if (boot->NumFatEntries < boot->NumClusters - CLUST_FIRST) {
 		pfatal("FAT size too small, %u entries won't fit into %u sectors\n",
 		       boot->NumClusters, boot->FATsecs);
 		return FSFATAL;