diff --git a/dali/python/nvidia/dali/data_node.py b/dali/python/nvidia/dali/data_node.py
index 8556778d23..76145d4106 100644
--- a/dali/python/nvidia/dali/data_node.py
+++ b/dali/python/nvidia/dali/data_node.py
@@ -152,6 +152,7 @@ def __getitem__(self, val):
         # returns True if this index adds a new output dimension
         def process_index(idx, dim):
             if idx is None:
+                print("DUPA!")
                 idxs.append((None, None, None, None))
                 return True
             elif isinstance(idx, slice):
@@ -164,6 +165,10 @@ def process_index(idx, dim):
                 if idx.name is not None:
                     new_axis_names.append(idx.name)
                 return True
+            elif idx is Ellipsis:
+                raise NotImplementedError("Ellipsis in indexing is not implemented")
+            elif isinstance(idx, (float, str)):
+                raise TypeError("Invalid type for an index: ", type)
             else:
                 idxs.append((idx, None, None, None))
                 return False
diff --git a/dali/test/python/test_dali_cpu_only.py b/dali/test/python/test_dali_cpu_only.py
index 88f827f634..f309214f58 100644
--- a/dali/test/python/test_dali_cpu_only.py
+++ b/dali/test/python/test_dali_cpu_only.py
@@ -89,9 +89,9 @@ def get_data():
     pipe.set_outputs(outs)
     assert_raises(RuntimeError, pipe.build)
 
-#def test_gpu_op_bad_device():
-#    for device_id in [None, 0]:
-#        yield check_bad_device, device_id
+def test_gpu_op_bad_device():
+    for device_id in [None, 0]:
+        yield check_bad_device, device_id
 
 def check_mixed_op_bad_device(device_id):
     pipe = Pipeline(batch_size=batch_size, num_threads=4, device_id=device_id)
@@ -100,9 +100,9 @@ def check_mixed_op_bad_device(device_id):
     pipe.set_outputs(decoded)
     assert_raises(RuntimeError, pipe.build)
 
-#def test_mixed_op_bad_device():
-#    for device_id in [None, 0]:
-#        yield check_bad_device, device_id
+def test_mixed_op_bad_device():
+    for device_id in [None, 0]:
+        yield check_bad_device, device_id
 
 def test_image_decoder_cpu():
     pipe = Pipeline(batch_size=batch_size, num_threads=4, device_id=None)
diff --git a/dali/test/python/test_operator_subscript.py b/dali/test/python/test_operator_subscript.py
index 52d05be338..6cf32abc48 100644
--- a/dali/test/python/test_operator_subscript.py
+++ b/dali/test/python/test_operator_subscript.py
@@ -172,3 +172,16 @@ def _test_too_many_indices(device):
 def test_too_many_indices():
     for device in ["cpu", "gpu"]:
         yield _test_too_many_indices, device
+
+def test_stride_not_implemented():
+    data = [np.uint8([1,2,3]),np.uint8([1,2])]
+    src = fn.external_source(lambda: data)
+    src[::1]
+    with assert_raises(NotImplementedError):
+        src[::2]
+
+def test_ellipsis_not_implemented():
+    data = [np.uint8([1,2,3]),np.uint8([1,2])]
+    src = fn.external_source(lambda: data)
+    with assert_raises(NotImplementedError):
+        src[...,:1]