diff --git a/src/service/oauth/grant.rs b/src/service/oauth/grant.rs
index f53c18600..d0bd66d0b 100644
--- a/src/service/oauth/grant.rs
+++ b/src/service/oauth/grant.rs
@@ -195,6 +195,7 @@ pub enum ErrorCode {
 	AccessDenied,
 	InvalidScope,
 	InvalidGrant,
+	InvalidClient,
 	InvalidClientMetadata,
 	AuthorizationPending,
 	ExpiredToken,
diff --git a/src/service/oauth/mod.rs b/src/service/oauth/mod.rs
index ba8958cfa..a999810ce 100644
--- a/src/service/oauth/mod.rs
+++ b/src/service/oauth/mod.rs
@@ -326,7 +326,7 @@ impl Service {
 		query: DeviceCodeRequest,
 	) -> Result<DeviceCodeResponse, OAuthError> {
 		let Some(client_metadata) = self.get_client_metadata(&query.client_id).await else {
-			return Err(OAuthError::invalid_grant("Invalid client ID"));
+			return Err(OAuthError::new_static(ErrorCode::InvalidClient, "Invalid client ID"));
 		};
 
 		let requested_scopes = query
@@ -434,7 +434,7 @@ impl Service {
 		let TokenRequest { client_id, request } = request;
 
 		let Some(client_metadata) = self.get_client_metadata(&client_id).await else {
-			return Err(OAuthError::invalid_request("Invalid client ID"));
+			return Err(OAuthError::new_static(ErrorCode::InvalidClient, "Invalid client ID"));
 		};
 
 		if !client_metadata.grant_types.contains(&request.grant_type()) {