diff --git a/hooks/luks/luks.init b/hooks/luks/luks.init
index 04b610d..193d2d8 100644
--- a/hooks/luks/luks.init
+++ b/hooks/luks/luks.init
@@ -11,7 +11,7 @@ mkdir -p /run/cryptsetup
 resolve_device "$luks_root"
 
 DM_DISABLE_UDEV=1 cryptsetup open \
-    "${luks_discard:+--allow-discards}" \
-    "${luks_header:+--header=$luks_header}" \
-    "${luks_key:+--key-file=$luks_key}" -- "$device" \
+    ${luks_discard:+--allow-discards} \
+    ${luks_header:+--header=$luks_header} \
+    ${luks_key:+--key-file=$luks_key} -- "$device" \
     "${luks_name:-crypt-${device##*/}}" || panic "failed to unlock LUKS"