--- /usr/share/initramfs-tools/scripts/zfs      2016-04-06 17:48:11.000000000 +0200
+++ /target/usr/share/initramfs-tools/scripts/zfs       2016-04-15 13:32:04.512421085 +0200
@@ -257,7 +257,7 @@
 
                        import_pool "${pool}" && \
                                rfs="$(find_rootfs "${pool}")" && \
-                                       ZFS_BOOTFS="${rfs}"
+                                       [ -z "${ZFS_BOOTFS}" ] && ZFS_BOOTFS="${rfs}"
                        [ -n "${ZFS_BOOTFS}" ] && break
                done
                IFS="${OLD_IFS}"
@@ -278,7 +278,7 @@
        then
                import_pool "${ZFS_RPOOL}" && \
                        rfs="$(find_rootfs "${ZFS_RPOOL}")" && \
-                               ZFS_BOOTFS="${rfs}"
+                               [ -z "${ZFS_BOOTFS}" ] && ZFS_BOOTFS="${rfs}"
        fi
 
        if [ -z "${POOL_IMPORTED}" ]