diff --git a/test/test_representations.py b/test/test_representations.py
index 4c26fe6a..b7c89373 100644
--- a/test/test_representations.py
+++ b/test/test_representations.py
@@ -173,6 +173,14 @@ def test_representation_inferred_frame():
     assert frames.shape[1:] == sensor_size[::-1]
 
 
+def test_representation_frame_wrong_sensor_size():
+    sensor_size = (20, 10, 2)
+    orig_events, _ = create_random_input(n_events=30000, sensor_size=sensor_size)
+    transform = transforms.ToFrame(sensor_size=(20, 10, 1), time_window=25000)
+    with pytest.raises(ValueError):
+        frames = transform(orig_events)
+
+
 def test_representation_audio_frame():
     sensor_size = (200, 1, 2)
     orig_events, _ = create_random_input(
diff --git a/tonic/functional/to_frame.py b/tonic/functional/to_frame.py
index 76ec3ed4..cd1bacdf 100644
--- a/tonic/functional/to_frame.py
+++ b/tonic/functional/to_frame.py
@@ -59,6 +59,10 @@ def to_frame_numpy(
 
     # test for single polarity
     if sensor_size[2] == 1:
+        if np.unique(events["p"]).size > 1:
+            raise ValueError(
+                "Single polarity sensor, but events contain both polarities."
+            )
         events["p"] = 0
 
     if time_window: