diff -urpN busybox-1.13.3/archival/libunarchive/get_header_tar.c busybox-1.13.3-tar/archival/libunarchive/get_header_tar.c
--- busybox-1.13.3/archival/libunarchive/get_header_tar.c	2009-02-26 12:46:40.000000000 +0100
+++ busybox-1.13.3-tar/archival/libunarchive/get_header_tar.c	2009-04-01 01:15:26.000000000 +0200
@@ -91,7 +91,7 @@ char FAST_FUNC get_header_tar(archive_ha
 
  again_after_align:
 
-#if ENABLE_DESKTOP
+#if ENABLE_DESKTOP || ENABLE_FEATURE_TAR_AUTODETECT
 	/* to prevent misdetection of bz2 sig */
 	*(uint32_t*)(&tar) = 0;
 	i = full_read(archive_handle->src_fd, &tar, 512);
@@ -142,7 +142,7 @@ char FAST_FUNC get_header_tar(archive_ha
 #if ENABLE_FEATURE_TAR_AUTODETECT
 		char FAST_FUNC (*get_header_ptr)(archive_handle_t *);
 
- USE_DESKTOP(autodetect:)
+ autodetect:
 		/* tar gz/bz autodetect: check for gz/bz2 magic.
 		 * If we see the magic, and it is the very first block,
 		 * we can switch to get_header_tar_gz/bz2/lzma().
diff -urpN busybox-1.13.3/archival/tar.c busybox-1.13.3-tar/archival/tar.c
--- busybox-1.13.3/archival/tar.c	2009-02-26 12:56:00.000000000 +0100
+++ busybox-1.13.3-tar/archival/tar.c	2009-04-01 01:15:39.000000000 +0200
@@ -934,8 +934,10 @@ int tar_main(int argc UNUSED_PARAM, char
 			tar_handle->src_fd = fileno(tar_stream);
 			tar_handle->seek = seek_by_read;
 		} else {
-			if (ENABLE_FEATURE_TAR_AUTODETECT && flags == O_RDONLY) {
-				get_header_ptr = get_header_tar;
+			if (ENABLE_FEATURE_TAR_AUTODETECT
+			 && get_header_ptr == get_header_tar
+			 && flags == O_RDONLY
+			) {
 				tar_handle->src_fd = open_zipped(tar_filename);
 				if (tar_handle->src_fd < 0)
 					bb_perror_msg_and_die("can't open '%s'", tar_filename);