diff --git a/frappe/model/document.py b/frappe/model/document.py
index e474a551c1..aeb8f6113c 100644
--- a/frappe/model/document.py
+++ b/frappe/model/document.py
@@ -602,9 +602,10 @@ class Document(BaseDocument):
 		self._action = "save"
 		if not self.get('__islocal'):
 			if self.meta.issingle:
-				modified = frappe.db.get_values_from_single(["modified"], "", self.doctype)
+				modified = frappe.db.sql('''select value from tabSingles
+					where doctype=%s and field='modified' for update''', self.doctype)
 				modified = modified and modified[0][0]
-				if modified and modified != self._original_modified:
+				if modified and modified != cstr(self._original_modified):
 					conflict = True
 			else:
 				tmp = frappe.db.sql("""select modified, docstatus from `tab{0}`
diff --git a/frappe/model/utils/__init__.py b/frappe/model/utils/__init__.py
index 2a62fa9142..a7b26b94f5 100644
--- a/frappe/model/utils/__init__.py
+++ b/frappe/model/utils/__init__.py
@@ -15,8 +15,8 @@ STANDARD_FIELD_CONVERSION_MAP = {
 	'name': 'Link',
 	'owner': 'Data',
 	'idx': 'Int',
-	'creation': 'Datetime',
-	'modified': 'Datetime',
+	'creation': 'Data',
+	'modified': 'Data',
 	'modified_by': 'Data',
 	'_user_tags': 'Data',
 	'_liked_by': 'Data',