--- a/sys/vfs/hammer2/hammer2_xops.c
+++ b/sys/vfs/hammer2/hammer2_xops.c
@@ -1579,7 +1579,15 @@
 			switch (chain->bref.type) {
 			case HAMMER2_BREF_TYPE_DIRENT:
 			case HAMMER2_BREF_TYPE_INODE:
-				KKASSERT(0);
+				/*
+				 * Crafted or corrupted media can place a
+				 * non-DATA chain under a regular-file inode.
+				 * Fail the truncation instead of panicking
+				 * (matches the CHECK error that
+				 * hammer2_chain_inode_find fabricates on
+				 * inconsistent media).
+				 */
+				error = HAMMER2_ERROR_CHECK;
 				break;
 			case HAMMER2_BREF_TYPE_DATA:
 				hammer2_chain_delete(parent, chain,