diff --git a/api/soap/mc_project_api.php b/api/soap/mc_project_api.php
index 9de79f6443..70fa36bb56 100644
--- a/api/soap/mc_project_api.php
+++ b/api/soap/mc_project_api.php
@@ -712,7 +712,7 @@ function mci_project_custom_fields_validate( $p_project_id, &$p_custom_fields )
 		    !custom_field_validate( $t_custom_field_id, $t_custom_field_values[$t_name] ) ) {
 			throw new ClientException(
 				"Invalid custom field '$t_name' value.",
-				ERROR_EMPTY_FIELD,
+				ERROR_CUSTOM_FIELD_INVALID_VALUE,
 				array( $t_name )
 			);
 		}