diff --git a/archival/tar.c b/archival/tar.c
index 4ab38db..4f25648 100644
--- a/archival/tar.c
+++ b/archival/tar.c
@@ -297,7 +297,8 @@
 	header.typeflag = type;
 	strcpy(header.name, "././@LongLink");
 	/* This sets mode/uid/gid/mtime to "00...00<NUL>" strings */
-	memset(header.mode, '0', sizeof(struct prefilled));
+	memset((char*)&header + offsetof(struct tar_header_t, mode), /* make gcc-9.x happy */
+			'0', sizeof(struct prefilled));
 	header.mode [sizeof(header.mode ) - 1] = '\0';
 	header.uid  [sizeof(header.uid  ) - 1] = '\0';
 	header.gid  [sizeof(header.gid  ) - 1] = '\0';