diff --git a/flepimop/gempyor_pkg/src/gempyor/utils.py b/flepimop/gempyor_pkg/src/gempyor/utils.py
index 8c76ffb5e..397bd0909 100644
--- a/flepimop/gempyor_pkg/src/gempyor/utils.py
+++ b/flepimop/gempyor_pkg/src/gempyor/utils.py
@@ -94,7 +94,7 @@ def read_df(
         )
     elif path.suffix == ".parquet":
         return pd.read_parquet(path, engine="pyarrow")
-    raise ValueError(
+    raise NotImplementedError(
         f"Invalid extension provided: '{path.suffix[1:]}'. Supported extensions are `.csv` or `.parquet`."
     )