diff -Naur a/configure.ac b/configure.ac
--- a/configure.ac	2021-03-16 14:45:58.000000000 +0200
+++ b/configure.ac	2021-03-23 07:45:06.875557286 +0200
@@ -47,13 +47,10 @@
 # Checks for header files.
 AC_CHECK_HEADERS([stdlib.h string.h stdio.h assert.h unistd.h linux/io_uring.h linux/aio_abi.h])
 
-# Check if zfs >= 0.8.0 is available (for direct I/O support).
-AC_CHECK_PROG(have_zfs, zfs, yes)
-AS_IF([test x"$have_zfs" = x"yes"],
-   [AX_COMPARE_VERSION($(cat /sys/module/zfs/version | cut -f 1 -d -), [ge], [0.8.0],
-       [AC_DEFINE(RAFT_HAVE_ZFS_WITH_DIRECT_IO)], [])
-   ],
-   [])
+# zfs support. We have 0.8.6 as stable in Gentoo, which is plenty above the required minimum.
+AC_ARG_WITH([zfs], AS_HELP_STRING([--with-zfs], [Build with zfs support (default: disabled)]))
+AS_IF([test "x$with_zfs" = "xyes"],
+   [AC_DEFINE(RAFT_HAVE_ZFS_WITH_DIRECT_IO)], [])
 
 # Checks for typedefs, structures, and compiler characteristics.
 AC_TYPE_SIZE_T