diff --git a/scylla-server-rust/src/controllers/car_command_controller.rs b/scylla-server-rust/src/controllers/car_command_controller.rs
index 4b59cfe9..d1646c6f 100644
--- a/scylla-server-rust/src/controllers/car_command_controller.rs
+++ b/scylla-server-rust/src/controllers/car_command_controller.rs
@@ -14,12 +14,13 @@ pub const CALYPSO_BIDIR_CMD_PREFIX: &str = "Calypso/Bidir/Command/";
 
 #[derive(Deserialize, Debug)]
 pub struct ConfigRequest {
-    pub data: Vec<f32>,
+    pub data: Option<Vec<f32>>,
 }
 
 /// This controller recieves two peices of info: the key from the path, and the list of float values from the query params
 /// The key is used in accordance with the calypso specification: a command_data object is sent over siren to CALYPSO_BIDIR_CMD_PREFIX/<key>
-/// That command_data object is processed and matched via the key to a YAML specification for the encoding and sending of a CAN message
+/// That command_data object is processed and matched via the key to a YAML specification for the encoding and sending of a CAN message.
+/// If the data is invalid, too short, etc. the default feild from the YAML is instead sent, as with when the car initially turns on before argos connects.
 /// TLDR: This triggers a command <key> with the values <data_query.0.data> for calypso to update the CAN packet sent to the bus.
 pub async fn send_config(
     Path(key): Path<String>,
@@ -37,7 +38,10 @@ pub async fn send_config(
 
     // create a payload object of the values to be parsed by calypso into a CAN packet
     let mut payload = CommandData::new();
-    payload.data = data_query.0.data;
+    // writing an empty protobuf is OK, that indicates to calypso that the default value should be used
+    if let Some(data) = data_query.0.data {
+        payload.data = data;
+    }
     let Ok(bytes) = payload.write_to_bytes() else {
         return Err(ScyllaError::ImpossibleEncoding);
     };