diff --git a/services/identity/src/constants.rs b/services/identity/src/constants.rs
--- a/services/identity/src/constants.rs
+++ b/services/identity/src/constants.rs
@@ -216,6 +216,11 @@
   pub const TUNNELBROKER_LOG: &str = "Tunnelbroker Error";
 }
 
+// Tonic Status Messages
+pub mod tonic_status_messages {
+  pub const UNEXPECTED_MESSAGE_DATA: &str = "unexpected_message_data";
+}
+
 // Tunnelbroker
 pub const TUNNELBROKER_GRPC_ENDPOINT: &str = "TUNNELBROKER_GRPC_ENDPOINT";
 pub const DEFAULT_TUNNELBROKER_ENDPOINT: &str = "http://localhost:50051";
diff --git a/services/identity/src/grpc_utils.rs b/services/identity/src/grpc_utils.rs
--- a/services/identity/src/grpc_utils.rs
+++ b/services/identity/src/grpc_utils.rs
@@ -5,6 +5,7 @@
 use tracing::warn;
 
 use crate::{
+  constants::tonic_status_messages,
   database::{DeviceListUpdate, DeviceRow, KeyPayload},
   ddb_utils::{DBIdentity, Identifier as DBIdentifier},
   device_list::SignedDeviceList,
@@ -186,7 +187,9 @@
       .device_key_upload()
       .and_then(|upload| upload.device_key_info.as_ref())
       .map(|info| info.payload.clone())
-      .ok_or_else(|| Status::invalid_argument("unexpected message data"))
+      .ok_or_else(|| {
+        Status::invalid_argument(tonic_status_messages::UNEXPECTED_MESSAGE_DATA)
+      })
   }
 
   fn payload_signature(&self) -> Result<String, Status> {
@@ -194,7 +197,9 @@
       .device_key_upload()
       .and_then(|upload| upload.device_key_info.as_ref())
       .map(|info| info.payload_signature.clone())
-      .ok_or_else(|| Status::invalid_argument("unexpected message data"))
+      .ok_or_else(|| {
+        Status::invalid_argument(tonic_status_messages::UNEXPECTED_MESSAGE_DATA)
+      })
   }
 
   fn content_prekey(&self) -> Result<String, Status> {
@@ -202,7 +207,9 @@
       .device_key_upload()
       .and_then(|upload| upload.content_upload.as_ref())
       .map(|prekey| prekey.prekey.clone())
-      .ok_or_else(|| Status::invalid_argument("unexpected message data"))
+      .ok_or_else(|| {
+        Status::invalid_argument(tonic_status_messages::UNEXPECTED_MESSAGE_DATA)
+      })
   }
 
   fn content_prekey_signature(&self) -> Result<String, Status> {
@@ -210,7 +217,9 @@
       .device_key_upload()
       .and_then(|upload| upload.content_upload.as_ref())
       .map(|prekey| prekey.prekey_signature.clone())
-      .ok_or_else(|| Status::invalid_argument("unexpected message data"))
+      .ok_or_else(|| {
+        Status::invalid_argument(tonic_status_messages::UNEXPECTED_MESSAGE_DATA)
+      })
   }
 
   fn notif_prekey(&self) -> Result<String, Status> {
@@ -218,7 +227,9 @@
       .device_key_upload()
       .and_then(|upload| upload.notif_upload.as_ref())
       .map(|prekey| prekey.prekey.clone())
-      .ok_or_else(|| Status::invalid_argument("unexpected message data"))
+      .ok_or_else(|| {
+        Status::invalid_argument(tonic_status_messages::UNEXPECTED_MESSAGE_DATA)
+      })
   }
 
   fn notif_prekey_signature(&self) -> Result<String, Status> {
@@ -226,27 +237,35 @@
       .device_key_upload()
       .and_then(|upload| upload.notif_upload.as_ref())
       .map(|prekey| prekey.prekey_signature.clone())
-      .ok_or_else(|| Status::invalid_argument("unexpected message data"))
+      .ok_or_else(|| {
+        Status::invalid_argument(tonic_status_messages::UNEXPECTED_MESSAGE_DATA)
+      })
   }
 
   fn one_time_content_prekeys(&self) -> Result<Vec<String>, Status> {
     self
       .device_key_upload()
       .map(|upload| upload.one_time_content_prekeys.clone())
-      .ok_or_else(|| Status::invalid_argument("unexpected message data"))
+      .ok_or_else(|| {
+        Status::invalid_argument(tonic_status_messages::UNEXPECTED_MESSAGE_DATA)
+      })
   }
 
   fn one_time_notif_prekeys(&self) -> Result<Vec<String>, Status> {
     self
       .device_key_upload()
       .map(|upload| upload.one_time_notif_prekeys.clone())
-      .ok_or_else(|| Status::invalid_argument("unexpected message data"))
+      .ok_or_else(|| {
+        Status::invalid_argument(tonic_status_messages::UNEXPECTED_MESSAGE_DATA)
+      })
   }
   fn device_type(&self) -> Result<i32, Status> {
     self
       .device_key_upload()
       .map(|upload| upload.device_type)
-      .ok_or_else(|| Status::invalid_argument("unexpected message data"))
+      .ok_or_else(|| {
+        Status::invalid_argument(tonic_status_messages::UNEXPECTED_MESSAGE_DATA)
+      })
   }
 }