diff --git a/sql/field.cc b/sql/field.cc
index 18ef77230f2..381a13c3263 100644
--- a/sql/field.cc
+++ b/sql/field.cc
@@ -6202,9 +6202,16 @@ Field *Field_string::new_field(MEM_ROOT *root, struct st_table *new_table)
     This is done to ensure that ALTER TABLE will convert old VARCHAR fields
     to now VARCHAR fields.
   */
-  return new Field_varstring(field_length, maybe_null(),
-                             field_name, new_table,
-                             charset());
+  Field *new_field= new Field_varstring(field_length, maybe_null(),
+                                        field_name, new_table,
+                                        charset());
+  /*
+    delayed_insert::get_local_table() needs a ptr copied from old table.
+    This is what other new_field() methods do too. The above method of
+    Field_varstring sets ptr to NULL.
+  */
+  new_field->ptr= ptr;
+  return new_field;
 }
 
 /****************************************************************************