diff --git a/frappe/__init__.py b/frappe/__init__.py
index ea05db6e52..f60c114fa7 100644
--- a/frappe/__init__.py
+++ b/frappe/__init__.py
@@ -14,7 +14,7 @@ import os, importlib, inspect, logging, json
 from .exceptions import *
 from .utils.jinja import get_jenv, get_template, render_template
 
-__version__ = "6.27.22"
+__version__ = "6.27.23"
 
 local = Local()
 
diff --git a/frappe/email/bulk.py b/frappe/email/bulk.py
index b6648fae03..504c50e3cb 100644
--- a/frappe/email/bulk.py
+++ b/frappe/email/bulk.py
@@ -11,6 +11,7 @@ from frappe.email.email_body import get_email, get_formatted_html
 from frappe.utils.verified_command import get_signed_params, verify_request
 from html2text import html2text
 from frappe.utils import get_url, nowdate, encode, now_datetime, add_days, split_emails, cstr
+from frappe.utils.scheduler import log
 
 class BulkLimitCrossedError(frappe.ValidationError): pass
 
@@ -256,56 +257,76 @@ def flush(from_test=False):
 		where datediff(curdate(), creation) > 3 and status='Not Sent'""", auto_commit=auto_commit)
 
 	for i in xrange(500):
-		email = frappe.db.sql("""select * from `tabBulk Email` where
-			status='Not Sent' and ifnull(send_after, "2000-01-01 00:00:00") < %s
-			order by priority desc, creation asc limit 1 for update""", now_datetime(), as_dict=1)
+		# don't use for update here, as it leads deadlocks
+		email = frappe.db.sql('''select * from `tabBulk Email`
+			where status='Not Sent' and (send_after is null or send_after < %(now)s)
+			order by priority desc, creation asc
+			limit 1''', { 'now': now_datetime() }, as_dict=True)
+
 		if email:
 			email = email[0]
 		else:
 			break
 
-		frappe.db.sql("""update `tabBulk Email` set status='Sending' where name=%s""",
-			(email["name"],), auto_commit=auto_commit)
+		send_one(email, smtpserver, auto_commit)
 
-		if email.communication:
-			frappe.get_doc('Communication', email.communication).set_delivery_status(commit=auto_commit)
+		# NOTE: removing commit here because we pass auto_commit
+		# finally:
+		# 	frappe.db.commit()
+
+def send_one(email, smtpserver=None, auto_commit=True, now=False):
+	status = frappe.db.sql('''select status from `tabBulk Email` where name=%s for update''', email.name)[0][0]
+	if status != 'Not Sent':
+		# rollback to release lock and return
+		frappe.db.rollback()
+		return
+
+	frappe.db.sql("""update `tabBulk Email` set status='Sending', modified=%s where name=%s""",
+		(now_datetime(), email["name"]), auto_commit=auto_commit)
+
+	if email.communication:
+		frappe.get_doc('Communication', email.communication).set_delivery_status(commit=auto_commit)
+
+	try:
+		if auto_commit:
+			if not smtpserver: smtpserver = SMTPServer()
+			smtpserver.setup_email_account(email.reference_doctype)
+			smtpserver.sess.sendmail(email["sender"], email["recipient"], encode(email["message"]))
 
-		try:
-			if not from_test:
-				smtpserver.setup_email_account(email.reference_doctype)
-				smtpserver.sess.sendmail(email["sender"], email["recipient"], encode(email["message"]))
+		frappe.db.sql("""update `tabBulk Email` set status='Sent', modified=%s where name=%s""",
+			(now_datetime(), email["name"]), auto_commit=auto_commit)
 
-			frappe.db.sql("""update `tabBulk Email` set status='Sent' where name=%s""",
-				(email["name"],), auto_commit=auto_commit)
+		if email.communication:
+			frappe.get_doc('Communication', email.communication).set_delivery_status(commit=auto_commit)
 
-			if email.communication:
-				frappe.get_doc('Communication', email.communication).set_delivery_status(commit=auto_commit)
+	except (smtplib.SMTPServerDisconnected,
+			smtplib.SMTPConnectError,
+			smtplib.SMTPHeloError,
+			smtplib.SMTPAuthenticationError):
 
-		except (smtplib.SMTPServerDisconnected,
-				smtplib.SMTPConnectError,
-				smtplib.SMTPHeloError,
-				smtplib.SMTPAuthenticationError):
+		# bad connection, retry later
+		frappe.db.sql("""update `tabBulk Email` set status='Not Sent', modified=%s where name=%s""",
+			(now_datetime(), email["name"]), auto_commit=auto_commit)
 
-			# bad connection, retry later
-			frappe.db.sql("""update `tabBulk Email` set status='Not Sent' where name=%s""",
-				(email["name"],), auto_commit=auto_commit)
+		if email.communication:
+			frappe.get_doc('Communication', email.communication).set_delivery_status(commit=auto_commit)
 
-			if email.communication:
-				frappe.get_doc('Communication', email.communication).set_delivery_status(commit=auto_commit)
+		# no need to attempt further
+		return
 
-			# no need to attempt further
-			return
+	except Exception, e:
+		frappe.db.sql("""update `tabBulk Email` set status='Error', error=%s
+			where name=%s""", (unicode(e), email["name"]), auto_commit=auto_commit)
 
-		except Exception, e:
-			frappe.db.sql("""update `tabBulk Email` set status='Error', error=%s
-				where name=%s""", (unicode(e), email["name"]), auto_commit=auto_commit)
+		if email.communication:
+			frappe.get_doc('Communication', email.communication).set_delivery_status(commit=auto_commit)
 
-			if email.communication:
-				frappe.get_doc('Communication', email.communication).set_delivery_status(commit=auto_commit)
+		if now:
+			raise
 
-		# NOTE: removing commit here because we pass auto_commit
-		# finally:
-		# 	frappe.db.commit()
+		else:
+			# log to scheduler log
+			log('frappe.email.bulk.flush', unicode(e))
 
 def clear_outbox():
 	"""Remove mails older than 31 days in Outbox. Called daily via scheduler."""
diff --git a/frappe/email/doctype/bulk_email/bulk_email.json b/frappe/email/doctype/bulk_email/bulk_email.json
index 4fe5154d2a..08cb9356fd 100644
--- a/frappe/email/doctype/bulk_email/bulk_email.json
+++ b/frappe/email/doctype/bulk_email/bulk_email.json
@@ -1,304 +1,304 @@
 {
- "allow_copy": 0, 
- "allow_import": 0, 
- "allow_rename": 0, 
- "autoname": "hash", 
- "creation": "2012-08-02 15:17:28", 
- "custom": 0, 
- "description": "Bulk Email records.", 
- "docstatus": 0, 
- "doctype": "DocType", 
- "document_type": "System", 
+ "allow_copy": 0,
+ "allow_import": 0,
+ "allow_rename": 0,
+ "autoname": "hash",
+ "creation": "2012-08-02 15:17:28",
+ "custom": 0,
+ "description": "Bulk Email records.",
+ "docstatus": 0,
+ "doctype": "DocType",
+ "document_type": "System",
  "fields": [
   {
-   "allow_on_submit": 0, 
-   "bold": 0, 
-   "collapsible": 0, 
-   "fieldname": "sender", 
-   "fieldtype": "Data", 
-   "hidden": 0, 
-   "ignore_user_permissions": 0, 
-   "ignore_xss_filter": 0, 
-   "in_filter": 0, 
-   "in_list_view": 0, 
-   "label": "Sender", 
-   "length": 0, 
-   "no_copy": 0, 
-   "options": "Email", 
-   "permlevel": 0, 
-   "print_hide": 0, 
-   "print_hide_if_no_value": 0, 
-   "read_only": 0, 
-   "report_hide": 0, 
-   "reqd": 0, 
-   "search_index": 0, 
-   "set_only_once": 0, 
+   "allow_on_submit": 0,
+   "bold": 0,
+   "collapsible": 0,
+   "fieldname": "sender",
+   "fieldtype": "Data",
+   "hidden": 0,
+   "ignore_user_permissions": 0,
+   "ignore_xss_filter": 0,
+   "in_filter": 0,
+   "in_list_view": 0,
+   "label": "Sender",
+   "length": 0,
+   "no_copy": 0,
+   "options": "Email",
+   "permlevel": 0,
+   "print_hide": 0,
+   "print_hide_if_no_value": 0,
+   "read_only": 0,
+   "report_hide": 0,
+   "reqd": 0,
+   "search_index": 0,
+   "set_only_once": 0,
    "unique": 0
-  }, 
+  },
   {
-   "allow_on_submit": 0, 
-   "bold": 0, 
-   "collapsible": 0, 
-   "fieldname": "recipient", 
-   "fieldtype": "Data", 
-   "hidden": 0, 
-   "ignore_user_permissions": 0, 
-   "ignore_xss_filter": 0, 
-   "in_filter": 0, 
-   "in_list_view": 1, 
-   "label": "Recipient", 
-   "length": 0, 
-   "no_copy": 0, 
-   "options": "Email", 
-   "permlevel": 0, 
-   "print_hide": 0, 
-   "print_hide_if_no_value": 0, 
-   "read_only": 0, 
-   "report_hide": 0, 
-   "reqd": 0, 
-   "search_index": 0, 
-   "set_only_once": 0, 
+   "allow_on_submit": 0,
+   "bold": 0,
+   "collapsible": 0,
+   "fieldname": "recipient",
+   "fieldtype": "Data",
+   "hidden": 0,
+   "ignore_user_permissions": 0,
+   "ignore_xss_filter": 0,
+   "in_filter": 0,
+   "in_list_view": 1,
+   "label": "Recipient",
+   "length": 0,
+   "no_copy": 0,
+   "options": "Email",
+   "permlevel": 0,
+   "print_hide": 0,
+   "print_hide_if_no_value": 0,
+   "read_only": 0,
+   "report_hide": 0,
+   "reqd": 0,
+   "search_index": 0,
+   "set_only_once": 0,
    "unique": 0
-  }, 
+  },
   {
-   "allow_on_submit": 0, 
-   "bold": 0, 
-   "collapsible": 0, 
-   "fieldname": "message", 
-   "fieldtype": "Code", 
-   "hidden": 0, 
-   "ignore_user_permissions": 0, 
-   "ignore_xss_filter": 0, 
-   "in_filter": 0, 
-   "in_list_view": 0, 
-   "label": "Message", 
-   "length": 0, 
-   "no_copy": 0, 
-   "permlevel": 0, 
-   "print_hide": 0, 
-   "print_hide_if_no_value": 0, 
-   "read_only": 0, 
-   "report_hide": 0, 
-   "reqd": 0, 
-   "search_index": 0, 
-   "set_only_once": 0, 
+   "allow_on_submit": 0,
+   "bold": 0,
+   "collapsible": 0,
+   "fieldname": "message",
+   "fieldtype": "Code",
+   "hidden": 0,
+   "ignore_user_permissions": 0,
+   "ignore_xss_filter": 0,
+   "in_filter": 0,
+   "in_list_view": 0,
+   "label": "Message",
+   "length": 0,
+   "no_copy": 0,
+   "permlevel": 0,
+   "print_hide": 0,
+   "print_hide_if_no_value": 0,
+   "read_only": 0,
+   "report_hide": 0,
+   "reqd": 0,
+   "search_index": 0,
+   "set_only_once": 0,
    "unique": 0
-  }, 
+  },
   {
-   "allow_on_submit": 0, 
-   "bold": 0, 
-   "collapsible": 0, 
-   "default": "Not Sent", 
-   "fieldname": "status", 
-   "fieldtype": "Select", 
-   "hidden": 0, 
-   "ignore_user_permissions": 0, 
-   "ignore_xss_filter": 0, 
-   "in_filter": 0, 
-   "in_list_view": 1, 
-   "label": "Status", 
-   "length": 0, 
-   "no_copy": 0, 
-   "options": "\nNot Sent\nSending\nSent\nError\nExpired", 
-   "permlevel": 0, 
-   "print_hide": 0, 
-   "print_hide_if_no_value": 0, 
-   "read_only": 0, 
-   "report_hide": 0, 
-   "reqd": 0, 
-   "search_index": 0, 
-   "set_only_once": 0, 
+   "allow_on_submit": 0,
+   "bold": 0,
+   "collapsible": 0,
+   "default": "Not Sent",
+   "fieldname": "status",
+   "fieldtype": "Select",
+   "hidden": 0,
+   "ignore_user_permissions": 0,
+   "ignore_xss_filter": 0,
+   "in_filter": 0,
+   "in_list_view": 1,
+   "label": "Status",
+   "length": 0,
+   "no_copy": 0,
+   "options": "\nNot Sent\nSending\nSent\nError\nExpired",
+   "permlevel": 0,
+   "print_hide": 0,
+   "print_hide_if_no_value": 0,
+   "read_only": 0,
+   "report_hide": 0,
+   "reqd": 0,
+   "search_index": 0,
+   "set_only_once": 0,
    "unique": 0
-  }, 
+  },
   {
-   "allow_on_submit": 0, 
-   "bold": 0, 
-   "collapsible": 0, 
-   "fieldname": "error", 
-   "fieldtype": "Code", 
-   "hidden": 0, 
-   "ignore_user_permissions": 0, 
-   "ignore_xss_filter": 0, 
-   "in_filter": 0, 
-   "in_list_view": 0, 
-   "label": "Error", 
-   "length": 0, 
-   "no_copy": 0, 
-   "permlevel": 0, 
-   "print_hide": 0, 
-   "print_hide_if_no_value": 0, 
-   "read_only": 0, 
-   "report_hide": 0, 
-   "reqd": 0, 
-   "search_index": 0, 
-   "set_only_once": 0, 
+   "allow_on_submit": 0,
+   "bold": 0,
+   "collapsible": 0,
+   "fieldname": "error",
+   "fieldtype": "Code",
+   "hidden": 0,
+   "ignore_user_permissions": 0,
+   "ignore_xss_filter": 0,
+   "in_filter": 0,
+   "in_list_view": 0,
+   "label": "Error",
+   "length": 0,
+   "no_copy": 0,
+   "permlevel": 0,
+   "print_hide": 0,
+   "print_hide_if_no_value": 0,
+   "read_only": 0,
+   "report_hide": 0,
+   "reqd": 0,
+   "search_index": 0,
+   "set_only_once": 0,
    "unique": 0
-  }, 
+  },
   {
-   "allow_on_submit": 0, 
-   "bold": 0, 
-   "collapsible": 0, 
-   "fieldname": "reference_doctype", 
-   "fieldtype": "Link", 
-   "hidden": 0, 
-   "ignore_user_permissions": 0, 
-   "ignore_xss_filter": 0, 
-   "in_filter": 0, 
-   "in_list_view": 0, 
-   "label": "Reference DocType", 
-   "length": 0, 
-   "no_copy": 0, 
-   "options": "DocType", 
-   "permlevel": 0, 
-   "print_hide": 0, 
-   "print_hide_if_no_value": 0, 
-   "read_only": 1, 
-   "report_hide": 0, 
-   "reqd": 0, 
-   "search_index": 0, 
-   "set_only_once": 0, 
+   "allow_on_submit": 0,
+   "bold": 0,
+   "collapsible": 0,
+   "fieldname": "reference_doctype",
+   "fieldtype": "Link",
+   "hidden": 0,
+   "ignore_user_permissions": 0,
+   "ignore_xss_filter": 0,
+   "in_filter": 0,
+   "in_list_view": 0,
+   "label": "Reference DocType",
+   "length": 0,
+   "no_copy": 0,
+   "options": "DocType",
+   "permlevel": 0,
+   "print_hide": 0,
+   "print_hide_if_no_value": 0,
+   "read_only": 1,
+   "report_hide": 0,
+   "reqd": 0,
+   "search_index": 0,
+   "set_only_once": 0,
    "unique": 0
-  }, 
+  },
   {
-   "allow_on_submit": 0, 
-   "bold": 0, 
-   "collapsible": 0, 
-   "fieldname": "reference_name", 
-   "fieldtype": "Data", 
-   "hidden": 0, 
-   "ignore_user_permissions": 0, 
-   "ignore_xss_filter": 0, 
-   "in_filter": 0, 
-   "in_list_view": 0, 
-   "label": "Reference DocName", 
-   "length": 0, 
-   "no_copy": 0, 
-   "permlevel": 0, 
-   "print_hide": 0, 
-   "print_hide_if_no_value": 0, 
-   "read_only": 1, 
-   "report_hide": 0, 
-   "reqd": 0, 
-   "search_index": 0, 
-   "set_only_once": 0, 
+   "allow_on_submit": 0,
+   "bold": 0,
+   "collapsible": 0,
+   "fieldname": "reference_name",
+   "fieldtype": "Data",
+   "hidden": 0,
+   "ignore_user_permissions": 0,
+   "ignore_xss_filter": 0,
+   "in_filter": 0,
+   "in_list_view": 0,
+   "label": "Reference DocName",
+   "length": 0,
+   "no_copy": 0,
+   "permlevel": 0,
+   "print_hide": 0,
+   "print_hide_if_no_value": 0,
+   "read_only": 1,
+   "report_hide": 0,
+   "reqd": 0,
+   "search_index": 0,
+   "set_only_once": 0,
    "unique": 0
-  }, 
+  },
   {
-   "allow_on_submit": 0, 
-   "bold": 0, 
-   "collapsible": 0, 
-   "fieldname": "communication", 
-   "fieldtype": "Link", 
-   "hidden": 0, 
-   "ignore_user_permissions": 0, 
-   "ignore_xss_filter": 0, 
-   "in_filter": 0, 
-   "in_list_view": 0, 
-   "label": "Communication", 
-   "length": 0, 
-   "no_copy": 0, 
-   "options": "Communication", 
-   "permlevel": 0, 
-   "precision": "", 
-   "print_hide": 0, 
-   "print_hide_if_no_value": 0, 
-   "read_only": 0, 
-   "report_hide": 0, 
-   "reqd": 0, 
-   "search_index": 0, 
-   "set_only_once": 0, 
+   "allow_on_submit": 0,
+   "bold": 0,
+   "collapsible": 0,
+   "fieldname": "communication",
+   "fieldtype": "Link",
+   "hidden": 0,
+   "ignore_user_permissions": 0,
+   "ignore_xss_filter": 0,
+   "in_filter": 0,
+   "in_list_view": 0,
+   "label": "Communication",
+   "length": 0,
+   "no_copy": 0,
+   "options": "Communication",
+   "permlevel": 0,
+   "precision": "",
+   "print_hide": 0,
+   "print_hide_if_no_value": 0,
+   "read_only": 0,
+   "report_hide": 0,
+   "reqd": 0,
+   "search_index": 0,
+   "set_only_once": 0,
    "unique": 0
-  }, 
+  },
   {
-   "allow_on_submit": 0, 
-   "bold": 0, 
-   "collapsible": 0, 
-   "fieldname": "send_after", 
-   "fieldtype": "Datetime", 
-   "hidden": 0, 
-   "ignore_user_permissions": 0, 
-   "ignore_xss_filter": 0, 
-   "in_filter": 0, 
-   "in_list_view": 0, 
-   "label": "Send After", 
-   "length": 0, 
-   "no_copy": 1, 
-   "permlevel": 0, 
-   "precision": "", 
-   "print_hide": 0, 
-   "print_hide_if_no_value": 0, 
-   "read_only": 1, 
-   "report_hide": 0, 
-   "reqd": 0, 
-   "search_index": 0, 
-   "set_only_once": 0, 
+   "allow_on_submit": 0,
+   "bold": 0,
+   "collapsible": 0,
+   "fieldname": "send_after",
+   "fieldtype": "Datetime",
+   "hidden": 0,
+   "ignore_user_permissions": 0,
+   "ignore_xss_filter": 0,
+   "in_filter": 0,
+   "in_list_view": 0,
+   "label": "Send After",
+   "length": 0,
+   "no_copy": 1,
+   "permlevel": 0,
+   "precision": "",
+   "print_hide": 0,
+   "print_hide_if_no_value": 0,
+   "read_only": 1,
+   "report_hide": 0,
+   "reqd": 0,
+   "search_index": 0,
+   "set_only_once": 0,
    "unique": 0
-  }, 
+  },
   {
-   "allow_on_submit": 0, 
-   "bold": 0, 
-   "collapsible": 0, 
-   "default": "1", 
-   "fieldname": "priority", 
-   "fieldtype": "Int", 
-   "hidden": 0, 
-   "ignore_user_permissions": 0, 
-   "ignore_xss_filter": 0, 
-   "in_filter": 0, 
-   "in_list_view": 0, 
-   "label": "Priority", 
-   "length": 0, 
-   "no_copy": 0, 
-   "permlevel": 0, 
-   "precision": "", 
-   "print_hide": 0, 
-   "print_hide_if_no_value": 0, 
-   "read_only": 1, 
-   "report_hide": 0, 
-   "reqd": 0, 
-   "search_index": 0, 
-   "set_only_once": 0, 
+   "allow_on_submit": 0,
+   "bold": 0,
+   "collapsible": 0,
+   "default": "1",
+   "fieldname": "priority",
+   "fieldtype": "Int",
+   "hidden": 0,
+   "ignore_user_permissions": 0,
+   "ignore_xss_filter": 0,
+   "in_filter": 0,
+   "in_list_view": 0,
+   "label": "Priority",
+   "length": 0,
+   "no_copy": 0,
+   "permlevel": 0,
+   "precision": "",
+   "print_hide": 0,
+   "print_hide_if_no_value": 0,
+   "read_only": 1,
+   "report_hide": 0,
+   "reqd": 0,
+   "search_index": 0,
+   "set_only_once": 0,
    "unique": 0
   }
- ], 
- "hide_heading": 0, 
- "hide_toolbar": 0, 
- "icon": "icon-envelope", 
- "idx": 1, 
- "in_create": 1, 
- "in_dialog": 0, 
- "is_submittable": 0, 
- "issingle": 0, 
- "istable": 0, 
- "max_attachments": 0, 
- "modified": "2016-04-18 05:13:07.741981", 
- "modified_by": "Administrator", 
- "module": "Email", 
- "name": "Bulk Email", 
- "owner": "Administrator", 
+ ],
+ "hide_heading": 0,
+ "hide_toolbar": 0,
+ "icon": "icon-envelope",
+ "idx": 1,
+ "in_create": 1,
+ "in_dialog": 0,
+ "is_submittable": 0,
+ "issingle": 0,
+ "istable": 0,
+ "max_attachments": 0,
+ "modified": "2016-04-18 05:13:07.741982",
+ "modified_by": "Administrator",
+ "module": "Email",
+ "name": "Bulk Email",
+ "owner": "Administrator",
  "permissions": [
   {
-   "amend": 0, 
-   "apply_user_permissions": 0, 
-   "cancel": 0, 
-   "create": 0, 
-   "delete": 1, 
-   "email": 1, 
-   "export": 0, 
-   "if_owner": 0, 
-   "import": 0, 
-   "permlevel": 0, 
-   "print": 1, 
-   "read": 1, 
-   "report": 1, 
-   "role": "System Manager", 
-   "set_user_permissions": 0, 
-   "share": 0, 
-   "submit": 0, 
+   "amend": 0,
+   "apply_user_permissions": 0,
+   "cancel": 0,
+   "create": 0,
+   "delete": 1,
+   "email": 1,
+   "export": 0,
+   "if_owner": 0,
+   "import": 0,
+   "permlevel": 0,
+   "print": 1,
+   "read": 1,
+   "report": 1,
+   "role": "System Manager",
+   "set_user_permissions": 0,
+   "share": 0,
+   "submit": 0,
    "write": 0
   }
- ], 
- "read_only": 0, 
- "read_only_onload": 0, 
+ ],
+ "read_only": 0,
+ "read_only_onload": 0,
  "sort_order": "DESC"
-}
\ No newline at end of file
+}
diff --git a/frappe/email/doctype/bulk_email/bulk_email.py b/frappe/email/doctype/bulk_email/bulk_email.py
index 7b8d37f3a7..e4a51222e2 100644
--- a/frappe/email/doctype/bulk_email/bulk_email.py
+++ b/frappe/email/doctype/bulk_email/bulk_email.py
@@ -15,3 +15,7 @@ def retry_sending(name):
 	if doc and doc.status == "Error":
 		doc.status = "Not Sent"
 		doc.save(ignore_permissions=True)
+
+def on_doctype_update():
+	"""Add index in `tabCommunication` for `(reference_doctype, reference_name)`"""
+	frappe.db.add_index('Bulk Email', ('status', 'send_after', 'priority', 'creation'), 'index_bulk_flush')
diff --git a/frappe/tasks.py b/frappe/tasks.py
index e0e651ab0d..3db70365c7 100644
--- a/frappe/tasks.py
+++ b/frappe/tasks.py
@@ -81,7 +81,9 @@ def get_required_queues(app, prefix=''):
 	ret = []
 	for site in get_sites():
 		ret.append('{}{}'.format(prefix, site))
-	ret.append(app.conf['CELERY_DEFAULT_QUEUE'])
+	if not prefix:
+		# default queue only for shortjob workers
+		ret.append(app.conf['CELERY_DEFAULT_QUEUE'])
 	return ret
 
 def is_site_in_maintenance_mode(queue, prefix):