diff --git a/sys/vfs/hammer2/hammer2_bulkfree.c b/sys/vfs/hammer2/hammer2_bulkfree.c
--- a/sys/vfs/hammer2/hammer2_bulkfree.c
+++ b/sys/vfs/hammer2/hammer2_bulkfree.c
@@ -724,7 +724,18 @@
 
 	bfi->sstop = cbinfo.sbase;
 
-	incr = bfi->sstop / (hmp->total_size / 10000);
+	/*
+	 * DF-0818 (defense-in-depth): the divisor `total_size / 10000` is 0
+	 * whenever total_size < 10000.  Mount validation currently requires
+	 * volu_size >= HAMMER2_VOLUME_ALIGN (8 MiB) which keeps this safe,
+	 * but the unguarded divide is a latent foot-gun.  Clamp the divisor
+	 * so any future relaxation of the size validation cannot surface a
+	 * #DE trap here.
+	 */
+	if (hmp->total_size < 10000)
+		incr = 10000;
+	else
+		incr = bfi->sstop / (hmp->total_size / 10000);
 	if (incr > 10000)
 		incr = 10000;