aliases+=(foo 'echo bar') crash

[Stephane Chazelas <stephane.chazelas@xxxxxxxxx>]

$ zsh --version
zsh 5.0.5 (x86_64-pc-linux-gnu)
$ zsh -c 'aliases+=(a b)'
*** Error in `zsh': double free or corruption (out): 0x00007f55e838f7e0 ***
zsh: abort      zsh -c 'aliases+=(a b)'

(gdb) bt
#0  0x00007ffff7135407 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
#1  0x00007ffff71367e8 in __GI_abort () at abort.c:89
#2  0x00007ffff7173394 in __libc_message (do_abort=do_abort@entry=1, fmt=fmt@entry=0x7ffff7266010 "*** Error in `%s': %s: 0x%s ***\n") at ../sysdeps/posix/libc_fatal.c:175
#3  0x00007ffff7178b6e in malloc_printerr (action=1, str=0x7ffff7266160 "double free or corruption (out)", ptr=<optimized out>) at malloc.c:4996
#4  0x00007ffff7179876 in _int_free (av=<optimized out>, p=<optimized out>, have_lock=0) at malloc.c:3840
#5  0x0000000000455305 in strsetfn ()
#6  0x000000000045a2f2 in ?? ()
#7  0x000000000045a7cc in arrhashsetfn ()
#8  0x000000000045b263 in assignaparam ()
#9  0x00000000004226cc in ?? ()
#10 0x00000000004272a5 in ?? ()
#11 0x0000000000428896 in ?? ()
#12 0x0000000000428c0e in ?? ()
#13 0x0000000000429db1 in execlist ()
#14 0x000000000042a030 in execode ()
#15 0x000000000042a102 in execstring ()
#16 0x000000000043bde2 in init_misc ()
#17 0x000000000043d29e in zsh_main ()
#18 0x00007ffff7121b45 in __libc_start_main (main=0x40f010 <main>, argc=3, argv=0x7fffffffdd98, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>,
    stack_end=0x7fffffffdd88) at libc-start.c:287
#19 0x000000000040f03e in _start ()