diff --git a/mysql-test/include/index_merge1.inc b/mysql-test/include/index_merge1.inc
index 96d66bbb579..a3a874a8ed2 100644
--- a/mysql-test/include/index_merge1.inc
+++ b/mysql-test/include/index_merge1.inc
@@ -407,3 +407,35 @@ explain select * from t3 where a=1 and b=1;
 drop table t3;
 drop table t0, t1, t2;
 }
+
+#
+# BUG#20256 - LOCK WRITE - MyISAM
+#
+CREATE TABLE t1(a INT);
+INSERT INTO t1 VALUES(1);
+CREATE TABLE t2(a INT, b INT, dummy CHAR(16) DEFAULT '', KEY(a), KEY(b));
+INSERT INTO t2(a,b) VALUES
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(1,2);
+LOCK TABLES t1 WRITE, t2 WRITE;
+INSERT INTO t2(a,b) VALUES(1,2);
+SELECT t2.a FROM t1,t2 WHERE t2.b=2 AND t2.a=1;
+UNLOCK TABLES;
+DROP TABLE t1, t2;
diff --git a/sql/ha_myisam.cc b/sql/ha_myisam.cc
index cbb8a7a48c0..3826a30e247 100644
--- a/sql/ha_myisam.cc
+++ b/sql/ha_myisam.cc
@@ -147,6 +147,14 @@ ha_myisam::ha_myisam(TABLE_SHARE *table_arg)
    can_enable_indexes(1)
 {}
 
+handler *ha_myisam::clone(MEM_ROOT *mem_root)
+{
+  ha_myisam *new_handler= static_cast <ha_myisam *>(handler::clone(mem_root));
+  if (new_handler)
+    new_handler->file->state= file->state;
+  return new_handler;
+}
+
 
 static const char *ha_myisam_exts[] = {
   ".MYI",
diff --git a/sql/ha_myisam.h b/sql/ha_myisam.h
index 5544e5040b3..511b796ebdb 100644
--- a/sql/ha_myisam.h
+++ b/sql/ha_myisam.h
@@ -45,6 +45,7 @@ class ha_myisam: public handler
  public:
   ha_myisam(TABLE_SHARE *table_arg);
   ~ha_myisam() {}
+  handler *clone(MEM_ROOT *mem_root);
   const char *table_type() const { return "MyISAM"; }
   const char *index_type(uint key_number);
   const char **bas_ext() const;
diff --git a/sql/handler.cc b/sql/handler.cc
index fbccfe7fa46..b787fad2f96 100644
--- a/sql/handler.cc
+++ b/sql/handler.cc
@@ -1416,6 +1416,15 @@ int ha_delete_table(THD *thd, handlerton *table_type, const char *path,
 /****************************************************************************
 ** General handler functions
 ****************************************************************************/
+handler *handler::clone(MEM_ROOT *mem_root)
+{
+  handler *new_handler= get_new_handler(table, mem_root, table->s->db_type);
+  if (new_handler && !new_handler->ha_open(table->s->path, table->db_stat,
+                                           HA_OPEN_IGNORE_IF_LOCKED))
+    return new_handler;
+  return NULL;
+}
+
 
 
 void handler::ha_statistic_increment(ulong SSV::*offset) const
diff --git a/sql/handler.h b/sql/handler.h
index 201a2f1980a..767990613f2 100644
--- a/sql/handler.h
+++ b/sql/handler.h
@@ -942,6 +942,7 @@ public:
   {
     /* TODO: DBUG_ASSERT(inited == NONE); */
   }
+  virtual handler *clone(MEM_ROOT *mem_root);
   /* This is called after create to allow us to set up cached variables */
   void init()
   {
diff --git a/sql/opt_range.cc b/sql/opt_range.cc
index a5a46ba11b6..30235154a89 100644
--- a/sql/opt_range.cc
+++ b/sql/opt_range.cc
@@ -1164,11 +1164,7 @@ int QUICK_RANGE_SELECT::init_ror_merged_scan(bool reuse_handler)
   }
 
   thd= head->in_use;
-  if (!(file= get_new_handler(head->s, thd->mem_root, head->s->db_type)))
-    goto failure;
-  DBUG_PRINT("info", ("Allocated new handler 0x%lx", (long) file));
-  if (file->ha_open(head, head->s->normalized_path.str, head->db_stat,
-                    HA_OPEN_IGNORE_IF_LOCKED))
+  if (!(file= head->file->clone(thd->mem_root)))
   {
     /* Caller will free the memory */
     goto failure;