diff --git a/docs/changelog.rst b/docs/changelog.rst
index b0275627..26a07167 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -4,6 +4,7 @@ Changelog
 
 Changes in 0.8.4
 ================
+- Fixed slice when using inheritance causing fields to be excluded (#437)
 - Fixed ._get_db() attribute after a Document.switch_db() (#441)
 - Dynamic Fields store and recompose Embedded Documents / Documents correctly (#449)
 - Handle dynamic fieldnames that look like digits (#434)
diff --git a/mongoengine/queryset/field_list.py b/mongoengine/queryset/field_list.py
index 73d3cc24..140a71e0 100644
--- a/mongoengine/queryset/field_list.py
+++ b/mongoengine/queryset/field_list.py
@@ -55,7 +55,8 @@ class QueryFieldList(object):
 
         if self.always_include:
             if self.value is self.ONLY and self.fields:
-                self.fields = self.fields.union(self.always_include)
+                if sorted(self.slice.keys()) != sorted(self.fields):
+                    self.fields = self.fields.union(self.always_include)
             else:
                 self.fields -= self.always_include