diff --git a/workflow/Snakefile b/workflow/Snakefile
index 346f081af9b112723e2627511a1691206f15f68b..8ffa4235b6e9eb13ba59f145a60ed7d084bd51a9 100644
--- a/workflow/Snakefile
+++ b/workflow/Snakefile
@@ -38,8 +38,8 @@ if missing:
     logger.error(err_msg)
     raise ValueError(err_msg)
 # Check if optional field available
-if 'optional' not in config or config['optional'] != dict:
-    logger.info(f'No "optional" field found or no valid configuration for config.yaml.')
+if 'optional' not in config or type(config['optional']) not in [OrderedDict, dict]:
+    logger.info(f'No "optional" field found or no valid configuration.')
     config['optional'] = {}
 # Check optional fields and include in config if not present
 for optkey, value in template_config['optional'].items():