diff --git a/sql/sql_window.cc b/sql/sql_window.cc
index 1568409fe04..bb95627ceae 100644
--- a/sql/sql_window.cc
+++ b/sql/sql_window.cc
@@ -9,6 +9,8 @@
 bool
 Window_spec::check_window_names(List_iterator_fast<Window_spec> &it)
 {
+  if (window_names_are_checked)
+    return false;
   char *name= this->name();
   char *ref_name= window_reference();
   it.rewind();
@@ -54,6 +56,7 @@ Window_spec::check_window_names(List_iterator_fast<Window_spec> &it)
     my_error(ER_WRONG_WINDOW_SPEC_NAME, MYF(0), ref_name);
     return true;              
   }
+  window_names_are_checked= true;
   return false;
 }
 
diff --git a/sql/sql_window.h b/sql/sql_window.h
index f5f4216f786..53bd19f8bd6 100644
--- a/sql/sql_window.h
+++ b/sql/sql_window.h
@@ -88,6 +88,8 @@ public:
 
 class Window_spec : public Sql_alloc
 {
+  bool window_names_are_checked;
+
  public:
 
   LEX_STRING *window_ref;
@@ -104,8 +106,9 @@ class Window_spec : public Sql_alloc
               SQL_I_List<ORDER> *part_list,
               SQL_I_List<ORDER> *ord_list,
               Window_frame *win_frame)
-    : window_ref(win_ref), partition_list(part_list), order_list(ord_list),
-    window_frame(win_frame), referenced_win_spec(NULL) {}
+    : window_names_are_checked(false), window_ref(win_ref),
+      partition_list(part_list), order_list(ord_list),
+      window_frame(win_frame), referenced_win_spec(NULL) {}
 
   virtual char *name() { return NULL; }