diff --git a/alioth/src/vfio/vfio.rs b/alioth/src/vfio/vfio.rs
index 256def1..3982c34 100644
--- a/alioth/src/vfio/vfio.rs
+++ b/alioth/src/vfio/vfio.rs
@@ -60,3 +60,13 @@ pub struct VfioParam {
     /// Path to the iommu device. [default: /dev/iommu]
     pub dev_iommu: Option<Box<Path>>,
 }
+
+#[derive(Debug, Deserialize, Help)]
+pub struct VfioParamLegacy {
+    /// Path to a VFIO group file, e.g. /dev/vfio/12.
+    pub group: Box<Path>,
+    /// Device ID, e.g. 0000:06:0d.0.
+    pub device: Box<str>,
+    /// Path to the vfio device. [default: /dev/vfio/vfio]
+    pub dev_vfio: Option<Box<Path>>,
+}
diff --git a/serde-aco/src/help.rs b/serde-aco/src/help.rs
index 88cd7c6..5990313 100644
--- a/serde-aco/src/help.rs
+++ b/serde-aco/src/help.rs
@@ -76,6 +76,7 @@ impl_help_for_types!(Bool, bool);
 impl_help_for_types!(
     String,
     &str,
+    Box<str>,
     String,
     CStr,
     CString,