diff --git a/src/logic/tpax_archive_write.c b/src/logic/tpax_archive_write.c
index b0dad94..2555d26 100644
--- a/src/logic/tpax_archive_write.c
+++ b/src/logic/tpax_archive_write.c
@@ -242,6 +242,12 @@ int tpax_archive_write(const struct tpax_driver_ctx * dctx)
 	return 0;
 }
 
+static int tpax_archive_seal_cpio(const struct tpax_driver_ctx * dctx)
+{
+	(void)dctx;
+	return -1;
+}
+
 int tpax_archive_seal(const struct tpax_driver_ctx * dctx)
 {
 	int     fdout;
@@ -249,37 +255,52 @@ int tpax_archive_seal(const struct tpax_driver_ctx * dctx)
 	ssize_t nbytes;
 	ssize_t nwritten;
 	ssize_t blksize;
-	char    buf[512];
+	char    buf[1024];
 
+	/* archive block size, current position */
 	blksize = dctx->cctx->blksize;
 	cpos    = tpax_get_driver_cpos(dctx);
 
+	/* internal error? */
 	if (cpos % 512)
 		return TPAX_CUSTOM_ERROR(dctx,TPAX_ERR_FLOW_ERROR);
 
+	/* cpio trailer? */
+	if (dctx->cctx->drvflags & TPAX_DRIVER_WRITE_FORMAT_CPIO)
+		return tpax_archive_seal_cpio(dctx);
+
+	/* ustar, pax */
 	fdout = tpax_driver_fdout(dctx);
 	memset(buf,0,sizeof(buf));
 
-	switch (cpos % blksize) {
-		case 0:
-			nbytes = cpos + blksize;
-			break;
+	if (tpax_archive_append_memory_data(fdout,buf,2*512) < 0)
+		return TPAX_SYSTEM_ERROR(dctx);
 
-		default:
-			nbytes  = cpos / blksize;
-			nbytes *= blksize;
-			nbytes += blksize;
+	cpos += 2*512;
 
-			if (nbytes-cpos == 512)
-				nbytes += blksize;
+	/* pax? */
+	if (dctx->cctx->drvflags & TPAX_DRIVER_WRITE_FORMAT_PAX) {
+		tpax_set_driver_cpos(dctx,cpos);
+		return 0;
 	}
 
-	for (nwritten=cpos; nwritten<nbytes; nwritten+=512) {
+	/* already at block boundary? */
+	if ((cpos % blksize) == 0) {
+		tpax_set_driver_cpos(dctx,cpos);
+		return 0;
+	}
+
+	/* zero-fill the remainder of the block */
+	nbytes  = cpos / blksize;
+	nbytes *= blksize;
+	nbytes += blksize;
+
+	for (nwritten=cpos; nwritten<nbytes; nwritten+=512)
 		if (tpax_archive_append_memory_data(fdout,buf,512) < 0)
 			return TPAX_SYSTEM_ERROR(dctx);
 
-		tpax_set_driver_cpos(dctx,nwritten);
-	}
+	/* all done */
+	tpax_set_driver_cpos(dctx,nwritten);
 
 	return 0;
 }