diff --git a/lib/libarchive/Makefile.inc b/lib/libarchive/Makefile.inc
index 153f96b12165..755a39ec01e8 100644
--- a/lib/libarchive/Makefile.inc
+++ b/lib/libarchive/Makefile.inc
@@ -1,23 +1,24 @@
 # These defines are needed for both libarchive and the tests. If we don't keep
 # them in sync we can get run-time crashes while running tests due to mismatches
 # between structures such as archive_md5_ctx, etc.
 
 LIBADD=	z bz2 lzma bsdxml zstd
 CFLAGS+=	-DHAVE_BZLIB_H=1 -DHAVE_LIBLZMA=1 -DHAVE_LZMA_H=1 \
-		-DHAVE_ZSTD_H=1 -DHAVE_LIBZSTD=1 -DHAVE_ZSTD_compressStream=1
+		-DHAVE_ZSTD_H=1 -DHAVE_LIBZSTD=1 -DHAVE_ZSTD_compressStream=1 \
+		-DHAVE_SYSCONF=1
 CFLAGS+=	-DPLATFORM_CONFIG_H=\"${.CURDIR}/config_freebsd.h\"
 
 .if ${MK_OPENSSL} != "no"
 CFLAGS+=	-DWITH_OPENSSL
 CFLAGS+=	-DOPENSSL_API_COMPAT=0x10100000L
 LIBADD+=	crypto
 CFLAGS.archive_hmac.c+=-Wno-error=cast-qual
 .else
 LIBADD+=	md
 .endif
 
 .if ${MK_ICONV} != "no"
 # TODO: This can be changed back to CFLAGS once iconv works correctly
 # with statically linked binaries.
 SHARED_CFLAGS+=	-DHAVE_ICONV=1 -DHAVE_ICONV_H=1 -DICONV_CONST=
 .endif