diff --git a/sql/item.cc b/sql/item.cc
index 34157c33cf4..6f1fdaae398 100644
--- a/sql/item.cc
+++ b/sql/item.cc
@@ -1,5 +1,5 @@
 /*
-   Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.
+   Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -1949,6 +1949,9 @@ Item_field::Item_field(Field *f)
    item_equal(0), no_const_subst(0),
    have_privileges(0), any_privileges(0)
 {
+  if (f->table->pos_in_table_list != NULL)
+    context= &(f->table->pos_in_table_list->select_lex->context);
+
   set_field(f);
   /*
     field_name and table_name should not point to garbage
diff --git a/sql/sql_union.cc b/sql/sql_union.cc
index d230b903d2c..ca6870dab9c 100644
--- a/sql/sql_union.cc
+++ b/sql/sql_union.cc
@@ -1,4 +1,4 @@
-/* Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved.
+/* Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -282,6 +282,19 @@ bool st_select_lex_unit::prepare(THD *thd_arg, select_result *sel_result,
       Item *item_tmp;
       while ((item_tmp= it++))
       {
+        /*
+          If the outer query has a GROUP BY clause, an outer reference to this
+          query block may have been wrapped in a Item_outer_ref, which has not
+          been fixed yet. An Item_type_holder must be created based on a fixed
+          Item, so use the inner Item instead.
+        */
+        DBUG_ASSERT(item_tmp->fixed ||
+                    (item_tmp->type() == Item::REF_ITEM &&
+                     ((Item_ref *)(item_tmp))->ref_type() ==
+                     Item_ref::OUTER_REF));
+        if (!item_tmp->fixed)
+          item_tmp= item_tmp->real_item();
+
 	/* Error's in 'new' will be detected after loop */
 	types.push_back(new Item_type_holder(thd_arg, item_tmp));
       }