diff --git a/nodebook/ipython/nodebookext.py b/nodebook/ipython/nodebookext.py
index 9e1c06b..8504092 100644
--- a/nodebook/ipython/nodebookext.py
+++ b/nodebook/ipython/nodebookext.py
@@ -67,7 +67,11 @@ def execute_cell(line, cell):
     ipython magic for executing nodebook cell, expects cell id and parent id inline, followed by code
     """
     assert NODEBOOK_STATE['nodebook'] is not None, "Nodebook not initialized, please use %nodebook {nodebook_name}"
-    cell_id, parent_id = line.lstrip().split(' ')
+    try:
+        cell_id, parent_id = line.lstrip().split(' ')
+    except ValueError:
+        cell_id = line.lstrip()
+        parent_id = None
 
     # make sure cell exists and is in the right position
     NODEBOOK_STATE['nodebook'].insert_node_after(cell_id, parent_id)
diff --git a/nodebook/pickledict.py b/nodebook/pickledict.py
index 33a32e3..3dc16bc 100644
--- a/nodebook/pickledict.py
+++ b/nodebook/pickledict.py
@@ -26,7 +26,7 @@
     from UserDict import DictMixin
 except ImportError:
     # see https://github.com/flask-restful/flask-restful/pull/231/files
-    from collections import MutableMapping as DictMixin
+    from collections.abc import MutableMapping as DictMixin
 
 PANDAS_CODE = 1
 CLOUDPICKLE_CODE = 2