Assertion `args[0]->fixed' fails in Item_func_conv_charset::Item_func_conv_charset

CREATE TABLE t1 (f1 VARCHAR(10) CHARSET utf8) ENGINE=MyISAM;

INSERT INTO t1 VALUES ('foo'),('bar');

CREATE TABLE t2 (f2 VARCHAR(10) CHARSET latin1) ENGINE=MyISAM;

INSERT INTO t2 VALUES  ('qux'),('foobar');

SELECT ( SELECT COUNT(*) FROM t1 WHERE f1 <= f2 ) AS sq

FROM t2 GROUP BY sq;

mysqld: 5.5/sql/item_strfunc.h:830: Item_func_conv_charset::Item_func_conv_charset(Item*, CHARSET_INFO*, bool): Assertion `args[0]->fixed' failed.

150323  0:10:05 [ERROR] mysqld got signal 6 ;

#6  0x00007f3d028de311 in *__GI___assert_fail (assertion=0xe0cdf8 "args[0]->fixed", file=<optimized out>, line=830, function=0xe10260 "Item_func_conv_charset::Item_func_conv_charset(Item*, CHARSET_INFO*, bool)") at assert.c:81

#7  0x00000000008135b1 in Item_func_conv_charset::Item_func_conv_charset (this=0x7f3cfd569f20, a=0x7f3cfd569de8, cs=0x1551240, cache_if_const=true) at 5.5/sql/item_strfunc.h:830

#8  0x00000000007f857f in Item::safe_charset_converter (this=0x7f3cfd569de8, tocs=0x1551240) at 5.5/sql/item.cc:1133

#9  0x00000000007fb460 in agg_item_set_converter (coll=..., fname=0xe114e2 "<=", args=0x7f3cfd688680, nargs=2, flags=7, item_sep=1) at 5.5/sql/item.cc:2181

#10 0x00000000007fb6ae in agg_item_charsets (coll=..., fname=0xe114e2 "<=", args=0x7f3cfd688680, nargs=2, flags=7, item_sep=1) at 5.5/sql/item.cc:2262

#11 0x000000000082a792 in agg_item_charsets_for_comparison (c=..., name=0xe114e2 "<=", items=0x7f3cfd688680, nitems=2, item_sep=1) at 5.5/sql/item.h:1906

#12 0x000000000082a898 in Item_func::agg_arg_charsets_for_comparison (this=0x7f3cfd6885f0, c=..., items=0x7f3cfd688680, nitems=2, item_sep=1) at 5.5/sql/item_func.h:217

#13 0x000000000081873a in Item_bool_func2::fix_length_and_dec (this=0x7f3cfd6885f0) at 5.5/sql/item_cmpfunc.cc:554

#14 0x000000000084291f in Item_func::fix_fields (this=0x7f3cfd6885f0, thd=0x7f3cfe550060, ref=0x7f3cfd569bd0) at 5.5/sql/item_func.cc:231

#15 0x00000000005e4000 in setup_conds (thd=0x7f3cfe550060, tables=0x7f3cfd687df8, leaves=..., conds=0x7f3cfd569bd0) at 5.5/sql/sql_base.cc:8894

#16 0x00000000006a4b0a in setup_without_group (thd=0x7f3cfe550060, ref_pointer_array=0x7f3cfd569cf8, tables=0x7f3cfd687df8, leaves=..., fields=..., all_fields=..., conds=0x7f3cfd569bd0, order=0x0, group=0x0, hidden_group_fields=0x7f3cfd569ab8) at 5.5/sql/sql_select.cc:577

#17 0x0000000000663d64 in JOIN::prepare (this=0x7f3cfd5697b8, rref_pointer_array=0x7f3cfd6873f8, tables_init=0x7f3cfd687df8, wild_num=0, conds_init=0x7f3cfd6885f0, og_num=0, order_init=0x0, skip_order_by=false, group_init=0x0, having_init=0x0, proc_param_init=0x0, select_lex_arg=0x7f3cfd687188, unit_arg=0x7f3cfd6874f8) at 5.5/sql/sql_select.cc:727

#18 0x0000000000883bca in subselect_single_select_engine::prepare (this=0x7f3cfd688898) at 5.5/sql/item_subselect.cc:3025

#19 0x000000000087c4bb in Item_subselect::fix_fields (this=0x7f3cfd688760, thd_param=0x7f3cfe550060, ref=0x7f3cfd6888e8) at 5.5/sql/item_subselect.cc:245

#20 0x00000000005e2328 in setup_fields (thd=0x7f3cfe550060, ref_pointer_array=0x7f3cfd569678, fields=..., mark_used_columns=MARK_COLUMNS_READ, sum_func_list=0x7f3cfd569468, allow_sum_func=true) at 5.5/sql/sql_base.cc:8169

#21 0x0000000000663cac in JOIN::prepare (this=0x7f3cfd569138, rref_pointer_array=0x7f3cfe553cd0, tables_init=0x7f3cfd688930, wild_num=0, conds_init=0x0, og_num=1, order_init=0x0, skip_order_by=false, group_init=0x7f3cfd689020, having_init=0x0, proc_param_init=0x0, select_lex_arg=0x7f3cfe553a60, unit_arg=0x7f3cfe553380) at 5.5/sql/sql_select.cc:723

#22 0x000000000066c3fb in mysql_select (thd=0x7f3cfe550060, rref_pointer_array=0x7f3cfe553cd0, tables=0x7f3cfd688930, wild_num=0, fields=..., conds=0x0, og_num=1, order=0x0, group=0x7f3cfd689020, having=0x0, proc_param=0x0, select_options=2147748608, result=0x7f3cfd569118, unit=0x7f3cfe553380, select_lex=0x7f3cfe553a60) at 5.5/sql/sql_select.cc:3074

#23 0x0000000000662f7d in handle_select (thd=0x7f3cfe550060, lex=0x7f3cfe5532d0, result=0x7f3cfd569118, setup_tables_done_option=0) at 5.5/sql/sql_select.cc:319

#24 0x000000000063c1bc in execute_sqlcom_select (thd=0x7f3cfe550060, all_tables=0x7f3cfd688930) at 5.5/sql/sql_parse.cc:4689

#25 0x000000000063539e in mysql_execute_command (thd=0x7f3cfe550060) at 5.5/sql/sql_parse.cc:2234

#26 0x000000000063eca2 in mysql_parse (thd=0x7f3cfe550060, rawbuf=0x7f3cfd687078 "SELECT ( SELECT COUNT(*) FROM t1 WHERE f1 <= f2 ) AS sq\nFROM t2 GROUP BY sq", length=75, parser_state=0x7f3cfdfb5620) at 5.5/sql/sql_parse.cc:5909

#27 0x00000000006328e5 in dispatch_command (command=COM_QUERY, thd=0x7f3cfe550060, packet=0x7f3cfe609061 "SELECT ( SELECT COUNT(*) FROM t1 WHERE f1 <= f2 ) AS sq\nFROM t2 GROUP BY sq", packet_length=75) at 5.5/sql/sql_parse.cc:1079

#28 0x0000000000631a71 in do_command (thd=0x7f3cfe550060) at 5.5/sql/sql_parse.cc:793

#29 0x00000000007340f2 in do_handle_one_connection (thd_arg=0x7f3cfe550060) at 5.5/sql/sql_connect.cc:1266

#30 0x0000000000733bb1 in handle_one_connection (arg=0x7f3cfe550060) at 5.5/sql/sql_connect.cc:1181

#31 0x0000000000b6c5f9 in pfs_spawn_thread (arg=0x7f3cfe571fc0) at 5.5/storage/perfschema/pfs.cc:1015

#32 0x00007f3d046d9b50 in start_thread (arg=<optimized out>) at pthread_create.c:304

#33 0x00007f3d0298f70d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:112