diff --git a/erpnext/communication/doctype/call_log/call_log.json b/erpnext/communication/doctype/call_log/call_log.json
index 3bc8dba..c3d6d07 100644
--- a/erpnext/communication/doctype/call_log/call_log.json
+++ b/erpnext/communication/doctype/call_log/call_log.json
@@ -75,10 +75,11 @@
   {
    "fieldname": "medium",
    "fieldtype": "Data",
-   "label": "Medium"
+   "label": "Medium",
+   "read_only": 1
   }
  ],
- "modified": "2019-06-17 08:21:20.665441",
+ "modified": "2019-06-17 09:02:48.150383",
  "modified_by": "Administrator",
  "module": "Communication",
  "name": "Call Log",
diff --git a/erpnext/communication/doctype/call_log/call_log.py b/erpnext/communication/doctype/call_log/call_log.py
index 0534706..66f1064 100644
--- a/erpnext/communication/doctype/call_log/call_log.py
+++ b/erpnext/communication/doctype/call_log/call_log.py
@@ -15,5 +15,5 @@
 
 	def on_update(self):
 		doc_before_save = self.get_doc_before_save()
-		if doc_before_save.status in ['Ringing'] and self.status in ['Missed', 'Completed']:
+		if doc_before_save and doc_before_save.status in ['Ringing'] and self.status in ['Missed', 'Completed']:
 			frappe.publish_realtime('call_{id}_disconnected'.format(id=self.id), self)