diff --git a/mapreader/spot_text/deepsolo_runner.py b/mapreader/spot_text/deepsolo_runner.py
index 4b7d0832..2793e2dc 100644
--- a/mapreader/spot_text/deepsolo_runner.py
+++ b/mapreader/spot_text/deepsolo_runner.py
@@ -33,7 +33,7 @@ class DeepSoloRunner(RecRunner):
     def __init__(
         self,
         patch_df: pd.DataFrame | gpd.GeoDataFrame | str | pathlib.Path,
-        parent_df: pd.DataFrame | gpd.GeoDataFrame | str | pathlib.Path = None,
+        parent_df: pd.DataFrame | gpd.GeoDataFrame | str | pathlib.Path | None = None,
         cfg_file: str
         | pathlib.Path = "./DeepSolo/configs/R_50/IC15/finetune_150k_tt_mlt_13_15_textocr.yaml",
         weights_file: str
diff --git a/mapreader/spot_text/dptext_detr_runner.py b/mapreader/spot_text/dptext_detr_runner.py
index c07873b2..343c50a9 100644
--- a/mapreader/spot_text/dptext_detr_runner.py
+++ b/mapreader/spot_text/dptext_detr_runner.py
@@ -35,7 +35,7 @@ class DPTextDETRRunner(Runner):
     def __init__(
         self,
         patch_df: pd.DataFrame | gpd.GeoDataFrame | str | pathlib.Path,
-        parent_df: pd.DataFrame | gpd.GeoDataFrame | str | pathlib.Path = None,
+        parent_df: pd.DataFrame | gpd.GeoDataFrame | str | pathlib.Path | None = None,
         cfg_file: str
         | pathlib.Path = "./DPText-DETR/configs/DPText_DETR/ArT/R_50_poly.yaml",
         weights_file: str | pathlib.Path = "./art_final.pth",
diff --git a/mapreader/spot_text/maptext_runner.py b/mapreader/spot_text/maptext_runner.py
index c56568e6..e2adbdf5 100644
--- a/mapreader/spot_text/maptext_runner.py
+++ b/mapreader/spot_text/maptext_runner.py
@@ -35,7 +35,7 @@ class MapTextRunner(RecRunner):
     def __init__(
         self,
         patch_df: pd.DataFrame | gpd.GeoDataFrame | str | pathlib.Path,
-        parent_df: pd.DataFrame | gpd.GeoDataFrame | str | pathlib.Path = None,
+        parent_df: pd.DataFrame | gpd.GeoDataFrame | str | pathlib.Path | None = None,
         cfg_file: str
         | pathlib.Path = "./MapTextPipeline/configs/ViTAEv2_S/rumsey/final_rumsey.yaml",
         weights_file: str | pathlib.Path = "./rumsey-finetune.pth",
diff --git a/mapreader/spot_text/runner_base.py b/mapreader/spot_text/runner_base.py
index bcdccf77..dc49c481 100644
--- a/mapreader/spot_text/runner_base.py
+++ b/mapreader/spot_text/runner_base.py
@@ -62,7 +62,10 @@ def _load_df(
                 "[ERROR] ``patch_df`` must be a path to a CSV/TSV/etc or geojson file, a pandas DataFrame or a geopandas GeoDataFrame."
             )
 
-        if isinstance(parent_df, pd.DataFrame):
+        if parent_df is None:
+            self.parent_df = pd.DataFrame()  # empty dataframe
+
+        elif isinstance(parent_df, pd.DataFrame):
             self.parent_df = parent_df
 
         elif isinstance(parent_df, (str, pathlib.Path)):