diff --git a/frappe/core/doctype/data_import/data_import.py b/frappe/core/doctype/data_import/data_import.py
index 1c56f54303..7e8374a0a2 100644
--- a/frappe/core/doctype/data_import/data_import.py
+++ b/frappe/core/doctype/data_import/data_import.py
@@ -211,7 +211,12 @@ def export_json(
 	doctype, path, filters=None, or_filters=None, name=None, order_by="creation asc"
 ):
 	def post_process(out):
-		del_keys = ("modified_by", "creation", "owner", "idx")
+		# Note on Tree DocTypes:
+		# The tree structure is maintained in the database via the fields "lft"
+		# and "rgt". They are automatically set and kept up-to-date. Importing
+		# them would destroy any existing tree structure. For this reason they
+		# are not exported as well.
+		del_keys = ("modified_by", "creation", "owner", "idx", "lft", "rgt")
 		for doc in out:
 			for key in del_keys:
 				if key in doc:
diff --git a/frappe/modules/import_file.py b/frappe/modules/import_file.py
index 5970eae5ca..fdfd00404c 100644
--- a/frappe/modules/import_file.py
+++ b/frappe/modules/import_file.py
@@ -107,6 +107,15 @@ def import_doc(docdict, force=False, data_import=False, pre_process=None,
 
 	doc = frappe.get_doc(docdict)
 
+	# Note on Tree DocTypes:
+	# The tree structure is maintained in the database via the fields "lft" and
+	# "rgt". They are automatically set and kept up-to-date. Importing them
+	# would destroy any existing tree structure.
+	if getattr(doc.meta, 'is_tree', None) and any([doc.lft, doc.rgt]):
+		print('Ignoring values of `lft` and `rgt` for {} "{}"'.format(doc.doctype, doc.name))
+		doc.lft = None
+		doc.rgt = None
+
 	doc.run_method("before_import")
 
 	doc.flags.ignore_version = ignore_version