panic: pmap_release: pmap resident count 1 != 0

bento was running 5.1-BETA from May 5, and it crashed overnight with:

panic: pmap_release: pmap resident count 1 != 0
cpuid = 1; lapic.id = 00000000
Dumping 1024 MB
 16 32[CTRL-C to abort] [CTRL-C to abort]  48 64 80 96 112 128 144 160 176 192 208 224 240 256 272 288 304 320 336 352 368 384 400 416 432 448 464 480 496 512 528 544 560 576 592 608 624 640 656 672 688 704 720 736 752 768 784 800 816 832 848 864 880 896 912 928 944 960 976 992 1008
---
#0  doadump () at ../../../kern/kern_shutdown.c:238
238             dumping++;
(kgdb) bt
#0  doadump () at ../../../kern/kern_shutdown.c:238
#1  0xc0142e15 in db_fncall (dummy1=1016, dummy2=0, dummy3=1016, dummy4=0xe2e8ba04 "") at ../../../ddb/db_command.c:546
#2  0xc0142b92 in db_command (last_cmdp=0xc0355c20, cmd_table=0x0, aux_cmd_tablep=0xc034fed0, aux_cmd_tablep_end=0xc034fed4)
    at ../../../ddb/db_command.c:346
#3  0xc0142ca6 in db_command_loop () at ../../../ddb/db_command.c:470
#4  0xc0145a2a in db_trap (type=3, code=0) at ../../../ddb/db_trap.c:72
#5  0xc02ecac4 in kdb_trap (type=3, code=0, regs=0xe2e8bb64) at ../../../i386/i386/db_interface.c:170
#6  0xc0305acc in trap (frame=
      {tf_fs = -1070071784, tf_es = 16, tf_ds = -959578096, tf_edi = -969572352, tf_esi = 256, tf_ebp = -488064080, tf_isp = -488064112, tf_ebx = 0, tf_edx = 0, tf_ecx = 1, tf_eax = 18, tf_trapno = 3, tf_err = 0, tf_eip = -1070674491, tf_cs = 8, tf_eflags = 646, tf_esp = -1070296208, tf_ss = -1070371997}) at ../../../i386/i386/trap.c:593
#7  0xc02ee478 in calltrap () at {standard input}:97
#8  0xc01b572f in panic (fmt=0x0) at ../../../kern/kern_shutdown.c:527
#9  0xc03018a1 in pmap_release (pmap=0xc82426b0) at ../../../i386/i386/pmap.c:1630
#10 0xc02ae2a7 in vmspace_exitfree (p=0xc6d16960) at vm_map.h:230
#11 0xc02ac300 in vm_waitproc (p=0xc6d16960) at ../../../vm/vm_glue.c:488
#12 0xc019f55e in wait1 (td=0xc6358000, uap=0xe2e8bd10, compat=0) at ../../../kern/kern_exit.c:687
#13 0xc019f070 in wait4 (td=0x0, uap=0x0) at ../../../kern/kern_exit.c:533
#14 0xc030641e in syscall (frame=
      {tf_fs = 47, tf_es = 47, tf_ds = 47, tf_edi = 1, tf_esi = 99286, tf_ebp = -1077938712, tf_isp = -488063628, tf_ebx = -1077938648, tf_edx = 2, tf_ecx = 0, tf_eax = 7, tf_trapno = 12, tf_err = 2, tf_eip = 134722971, tf_cs = 31, tf_eflags = 642, tf_esp = -1077938740, tf_ss = 47}) at ../../../i386/i386/trap.c:1028
#15 0xc02ee4cd in Xint0x80_syscall () at {standard input}:139
---Can't read userspace from dump, or kernel process---

(kgdb)

Is this already fixed?