diff --git a/src/fibad/config_utils.py b/src/fibad/config_utils.py
index 0d7a19b..291153b 100644
--- a/src/fibad/config_utils.py
+++ b/src/fibad/config_utils.py
@@ -265,7 +265,7 @@ def resolve_runtime_config(runtime_config_filepath: Union[Path, str, None] = Non
         return runtime_config_filepath
 
 
-def create_results_dir(config: ConfigDict, postfix: Union[Path, str]) -> Path:
+def create_results_dir(config: ConfigDict, postfix: str) -> Path:
     """Creates a results directory for this run.
 
     Postfix is the verb name of the run e.g. (infer, train, etc)