diff --git a/setup/doctype/company/company.py b/setup/doctype/company/company.py
index e383fb1bc8..9863d7d28b 100644
--- a/setup/doctype/company/company.py
+++ b/setup/doctype/company/company.py
@@ -16,6 +16,7 @@
 
 from __future__ import unicode_literals
 import webnotes
+from webnotes import _, msgprint
 
 from webnotes.utils import cstr
 from webnotes.model.doc import Document
@@ -288,6 +289,9 @@ class DocType:
 			and value=%s""", self.doc.name)
 			
 	def on_rename(self,newdn,olddn, merge=False):
+		if merge:
+			msgprint(_("Sorry. Companies cannot be merged"), raise_exception=True)
+		
 		webnotes.conn.sql("""update `tabCompany` set company_name=%s
 			where name=%s""", (newdn, olddn))
 		
diff --git a/stock/doctype/serial_no/serial_no.py b/stock/doctype/serial_no/serial_no.py
index e85a947899..501b535c6e 100644
--- a/stock/doctype/serial_no/serial_no.py
+++ b/stock/doctype/serial_no/serial_no.py
@@ -19,7 +19,7 @@ import webnotes
 
 from webnotes.utils import cint, getdate, nowdate
 import datetime
-from webnotes import msgprint
+from webnotes import msgprint, _
 	
 from controllers.stock_controller import StockController
 
@@ -119,6 +119,9 @@ class DocType(StockController):
 	
 	def on_rename(self, new, old, merge=False):
 		"""rename serial_no text fields"""
+		if merge:
+			msgprint(_("Sorry. Serial Nos. cannot be merged"), raise_exception=True)
+		
 		for dt in webnotes.conn.sql("""select parent from tabDocField 
 			where fieldname='serial_no' and fieldtype='Text'"""):