diff --git a/rust/src/model_ext.rs b/rust/src/model_ext.rs
index 632bfc76c..7c258f4c5 100644
--- a/rust/src/model_ext.rs
+++ b/rust/src/model_ext.rs
@@ -1,8 +1,10 @@
 //! Extensions of the auto-generated "models" (schema structs).
 
+use std::str::FromStr;
+
 use serde_json::json;
 
-use crate::models::MessageIn;
+use crate::{api::Ordering, models::MessageIn};
 
 impl MessageIn {
     /// Create a new message with a pre-serialized payload.
@@ -38,3 +40,19 @@ impl MessageIn {
         self
     }
 }
+
+#[derive(Debug, thiserror::Error)]
+#[error("invalid value for ordering")]
+pub struct OrderingFromStrError;
+
+impl FromStr for Ordering {
+    type Err = OrderingFromStrError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s {
+            "ascending" => Ok(Self::Ascending),
+            "descending" => Ok(Self::Descending),
+            _ => Err(OrderingFromStrError),
+        }
+    }
+}