diff --git a/lib/libarchive/archive_crc32.h b/lib/libarchive/archive_crc32.h
new file mode 100644
index 000000000000..771575476d98
--- /dev/null
+++ b/lib/libarchive/archive_crc32.h
@@ -0,0 +1,66 @@
+/*-
+ * Copyright (c) 2009 Joerg  Sonnenberger
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ */
+
+#ifndef __LIBARCHIVE_BUILD
+#error This header is only to be used internally to libarchive.
+#endif
+
+/*
+ * When zlib is unavailable, we should still be able to validate
+ * uncompressed zip archives.  That requires us to be able to compute
+ * the CRC32 check value.  This is a drop-in compatible replacement
+ * for crc32() from zlib.  It's slower than the zlib implementation,
+ * but still pretty fast: This runs about 300MB/s on my 3GHz P4
+ * compared to about 800MB/s for the zlib implementation.
+ */
+static unsigned long
+crc32(unsigned long crc, const void *_p, size_t len)
+{
+	unsigned long crc2, b, i;
+	const unsigned char *p = _p;
+	static volatile int crc_tbl_inited = 0;
+	static unsigned long crc_tbl[256];
+
+	if (!crc_tbl_inited) {
+		for (b = 0; b < 256; ++b) {
+			crc2 = b;
+			for (i = 8; i > 0; --i) {
+				if (crc2 & 1)
+					crc2 = (crc2 >> 1) ^ 0xedb88320UL;
+				else    
+					crc2 = (crc2 >> 1);
+			}
+			crc_tbl[b] = crc2;
+		}
+		crc_tbl_inited = 1;
+	}
+
+	crc = crc ^ 0xffffffffUL;
+	while (len--)
+		crc = crc_tbl[(crc ^ *p++) & 0xff] ^ (crc >> 8);
+	return (crc ^ 0xffffffffUL);
+}
diff --git a/lib/libarchive/archive_read_support_format_zip.c b/lib/libarchive/archive_read_support_format_zip.c
index ccb675d36749..4a24cc80930b 100644
--- a/lib/libarchive/archive_read_support_format_zip.c
+++ b/lib/libarchive/archive_read_support_format_zip.c
@@ -36,10 +36,6 @@ __FBSDID("$FreeBSD$");
 #include <time.h>
 #ifdef HAVE_ZLIB_H
 #include <zlib.h>
-#else
-/* Hmmm... This is necessary, but means that we can't correctly extract
- * even uncompressed entries on platforms that lack zlib. */
-#define	crc32(crc, buf, len) (unsigned long)0
 #endif
 
 #include "archive.h"
@@ -48,6 +44,10 @@ __FBSDID("$FreeBSD$");
 #include "archive_read_private.h"
 #include "archive_endian.h"
 
+#ifndef HAVE_ZLIB_H
+#include "archive_crc32.h"
+#endif
+
 struct zip {
 	/* entry_bytes_remaining is the number of bytes we expect. */
 	int64_t			entry_bytes_remaining;
@@ -540,8 +540,7 @@ archive_read_format_zip_read_data(struct archive_read *a,
 		return (r);
 	/* Update checksum */
 	if (*size)
-		zip->entry_crc32 =
-		    crc32(zip->entry_crc32, *buff, *size);
+		zip->entry_crc32 = crc32(zip->entry_crc32, *buff, *size);
 	/* If we hit the end, swallow any end-of-data marker. */
 	if (zip->end_of_entry) {
 		if (zip->flags & ZIP_LENGTH_AT_END) {