diff --git a/docs/points_to_geojson.md b/docs/points_to_geojson.md
index de2554a..57b5b39 100644
--- a/docs/points_to_geojson.md
+++ b/docs/points_to_geojson.md
@@ -7,7 +7,7 @@ Using a Napari or PlantCV-annotate viewer object with clicked points, output a s
 - **Parameters:**
     - img - Spectral image object, likely read in with [`geo.read_geotif`](read_geotif.md)
     - viewer - Napari viewer class object or plantcv-annotate Points class object.
-    - out_path - Path to save the geojson shapefile.
+    - out_path - Path to save the geojson shapefile. Must be ".geojson" file type. 
 
 - **Context:**
     - Saved points can be used downstream for generating circular ROIs or circles for use with rasterstats. 
diff --git a/plantcv/geospatial/points_to_geojson.py b/plantcv/geospatial/points_to_geojson.py
index 0571502..f64eb86 100644
--- a/plantcv/geospatial/points_to_geojson.py
+++ b/plantcv/geospatial/points_to_geojson.py
@@ -15,7 +15,7 @@ def points_to_geojson(img, viewer, out_path):
     viewer: Napari viewer class object or plantcv-annotate Points class object.
         The viewer used to make the clicks.
     out_path : str
-        Path to save to shapefile.
+        Path to save to shapefile. Must have "geojson" file extension
     """
     # Napari output, points must be reversed
     if hasattr(viewer, 'layers'):
diff --git a/tests/test_geospatial_points_to_geojson.py b/tests/test_geospatial_points_to_geojson.py
index 9042971..d06d1fe 100644
--- a/tests/test_geospatial_points_to_geojson.py
+++ b/tests/test_geospatial_points_to_geojson.py
@@ -42,3 +42,13 @@ def test_geospatial_points_to_geojson_badviewer(test_data, tmpdir):
     filename = os.path.join(cache_dir, 'test_out.geojson')
     with pytest.raises(RuntimeError):
         points_to_geojson(img, viewer, out_path=filename)
+    
+def test_geospatial_points_to_geojson_badfilename(test_data, tmpdir):
+    """Test for plantcv-geospatial."""
+    cache_dir = tmpdir.mkdir("cache")
+    img = read_geotif(filename=test_data.rgb_tif, bands="R,G,B")
+    viewer = FakePoints()
+    viewer.coords["default"] = []
+    filename = os.path.join(cache_dir, 'test_out.txt')
+    with pytest.raises(RuntimeError):
+        points_to_geojson(img, viewer, out_path=filename)