diff --git a/mysql-test/main/subselect4.result b/mysql-test/main/subselect4.result
index c0c67707231c4..2e6d57c68fd14 100644
--- a/mysql-test/main/subselect4.result
+++ b/mysql-test/main/subselect4.result
@@ -3372,5 +3372,11 @@ drop table t1,t2,t3;
 CREATE TABLE t(c INT);
 SELECT (SELECT 0 GROUP BY c HAVING (SELECT c)) FROM t GROUP BY c;
 (SELECT 0 GROUP BY c HAVING (SELECT c))
+#
+# MDEV-31632 Unresolvable outer reference causes null pointer exception
+#
+SELECT 1 union select 2 UNION SELECT 1 from t JOIN t b ON
+(SELECT 1 FROM dual WHERE AAA);
+ERROR 42S22: Unknown column 'AAA' in 'WHERE'
 DROP TABLE t;
 # End of 10.11 tests
diff --git a/mysql-test/main/subselect4.test b/mysql-test/main/subselect4.test
index 083da1647b27c..f3d68aae1739f 100644
--- a/mysql-test/main/subselect4.test
+++ b/mysql-test/main/subselect4.test
@@ -2693,6 +2693,15 @@ drop table t1,t2,t3;
 
 CREATE TABLE t(c INT);
 SELECT (SELECT 0 GROUP BY c HAVING (SELECT c)) FROM t GROUP BY c;
+
+--echo #
+--echo # MDEV-31632 Unresolvable outer reference causes null pointer exception
+--echo #
+
+--error ER_BAD_FIELD_ERROR
+SELECT 1 union select 2 UNION SELECT 1 from t JOIN t b ON
+  (SELECT 1 FROM dual WHERE AAA);
+
 DROP TABLE t;
 
 --echo # End of 10.11 tests
diff --git a/sql/item.cc b/sql/item.cc
index da3219d7545e4..b584df6912133 100644
--- a/sql/item.cc
+++ b/sql/item.cc
@@ -5922,10 +5922,19 @@ Item_field::fix_outer_field(THD *thd, Field **from_field, Item **reference)
     select= outer_context->select_lex;
     Item_subselect *prev_subselect_item=
       last_checked_context->select_lex->master_unit()->item;
+    /*
+      We have merged to the top select and this field is no longer outer,
+      or we have reached the outermost select without resolution
+    */
+    bool at_top= !prev_subselect_item;
     last_checked_context= outer_context;
     upward_lookup= TRUE;
 
-    place= prev_subselect_item->parsing_place;
+    if (!at_top)
+      place= prev_subselect_item->parsing_place;
+    else
+      place= NO_MATTER;
+
     /*
       If outer_field is set, field was already found by first call
       to find_field_in_tables(). Only need to find appropriate context.
@@ -5980,8 +5989,11 @@ Item_field::fix_outer_field(THD *thd, Field **from_field, Item **reference)
         }
         if (*from_field != view_ref_found)
         {
-          prev_subselect_item->used_tables_cache|= (*from_field)->table->map;
-          prev_subselect_item->const_item_cache= 0;
+          if (!at_top)
+          {
+            prev_subselect_item->used_tables_cache|= (*from_field)->table->map;
+            prev_subselect_item->const_item_cache= 0;
+          }
           set_field(*from_field);
           if (!last_checked_context->select_lex->having_fix_field &&
               select->group_list.elements &&
@@ -6030,7 +6042,8 @@ Item_field::fix_outer_field(THD *thd, Field **from_field, Item **reference)
         else
         {
           Item::Type ref_type= (*reference)->type();
-          prev_subselect_item->used_tables_and_const_cache_join(*reference);
+          if (!at_top)
+            prev_subselect_item->used_tables_and_const_cache_join(*reference);
           mark_as_dependent(thd, last_checked_context->select_lex,
                             context->select_lex, this,
                             ((ref_type == REF_ITEM || ref_type == FIELD_ITEM) ?
@@ -6064,7 +6077,8 @@ Item_field::fix_outer_field(THD *thd, Field **from_field, Item **reference)
       if (ref != not_found_item)
       {
         DBUG_ASSERT(*ref && (*ref)->fixed());
-        prev_subselect_item->used_tables_and_const_cache_join(*ref);
+        if (!at_top)
+          prev_subselect_item->used_tables_and_const_cache_join(*ref);
         break;
       }
     }
@@ -6074,8 +6088,11 @@ Item_field::fix_outer_field(THD *thd, Field **from_field, Item **reference)
       outer select (or we just trying to find wrong identifier, in this
       case it does not matter which used tables bits we set)
     */
-    prev_subselect_item->used_tables_cache|= OUTER_REF_TABLE_BIT;
-    prev_subselect_item->const_item_cache= 0;
+    if (!at_top)
+    {
+      prev_subselect_item->used_tables_cache|= OUTER_REF_TABLE_BIT;
+      prev_subselect_item->const_item_cache= 0;
+    }
   }
 
   DBUG_ASSERT(ref != 0);