diff --git a/accounts/doctype/c_form/c_form.py b/accounts/doctype/c_form/c_form.py
index bff68f7..1bea635 100644
--- a/accounts/doctype/c_form/c_form.py
+++ b/accounts/doctype/c_form/c_form.py
@@ -59,7 +59,7 @@
 				
 			webnotes.conn.sql("""update `tabSales Invoice` set c_form_no = '', modified = %s 
 				where name not in (%s) and ifnull(c_form_no, '') = %s""" % 
-				('%s', ', '.join(['%s'*len(inv)]), '%s'),
+				('%s', ', '.join(['%s']*len(inv)), '%s'),
 				tuple([self.doc.modified] + inv + [self.doc.name]), debug=1)
 		else:
 			webnotes.msgprint("Please enter atleast 1 invoice in the table", raise_exception=1)