fix: Validation for group cost center
diff --git a/erpnext/accounts/doctype/gl_entry/gl_entry.py b/erpnext/accounts/doctype/gl_entry/gl_entry.py
index 291aff3..645da34 100644
--- a/erpnext/accounts/doctype/gl_entry/gl_entry.py
+++ b/erpnext/accounts/doctype/gl_entry/gl_entry.py
@@ -4,7 +4,7 @@
 from __future__ import unicode_literals
 import frappe, erpnext
 from frappe import _
-from frappe.utils import flt, fmt_money, getdate, formatdate
+from frappe.utils import flt, fmt_money, getdate, formatdate, cint
 from frappe.model.document import Document
 from frappe.model.naming import set_name_from_naming_options
 from frappe.model.meta import get_field_precision
@@ -134,10 +134,17 @@
 
 			return self.cost_center_company[self.cost_center]
 
+		def _check_is_group():
+			return cint(frappe.get_cached_value('Cost Center', self.cost_center, 'is_group'))
+
 		if self.cost_center and _get_cost_center_company() != self.company:
 			frappe.throw(_("{0} {1}: Cost Center {2} does not belong to Company {3}")
 				.format(self.voucher_type, self.voucher_no, self.cost_center, self.company))
 
+		if self.cost_center and _check_is_group():
+			frappe.throw(_("""{0} {1}: Cost Center {2} is a group cost center and group cost centers cannot
+				be used in transactions""").format(self.voucher_type, self.voucher_no, frappe.bold(self.cost_center)))
+
 	def validate_party(self):
 		validate_party_frozen_disabled(self.party_type, self.party)