diff --git a/src/src/string.c b/src/src/string.c
index 5e48b445c..c6549bf93 100644
--- a/src/src/string.c
+++ b/src/src/string.c
@@ -224,6 +224,8 @@ interpreted in strings.
 Arguments:
   pp       points a pointer to the initiating "\" in the string;
            the pointer gets updated to point to the final character
+           If the backslash is the last character in the string, it
+           is not interpreted.
 Returns:   the value of the character escape
 */

@@ -236,6 +238,7 @@ const uschar *hex_digits= CUS"0123456789abcdef";
 int ch;
 const uschar *p = *pp;
 ch = *(++p);
+if (ch == '\0') return **pp;
 if (isdigit(ch) && ch != '8' && ch != '9')
   {
   ch -= '0';

len = Ustrlen(s) + 1;
ss = store_get(len);

while (*p)
  {
  if (*p == '\\')
    {
    *q++ = string_interpret_escape((const uschar **)&p);
    p++;
    }
 [...]
 }

gdb --args /usr/sbin/exim4 -q
gef➤  set follow-fork-mode child
gef➤  b string_unprinting
Breakpoint 1 at 0x5600d5924540: file string.c, line 355.
gef➤  r
Thread 2.1 "exim4" hit Breakpoint 1, string_unprinting (s=0x562b1a097790 "abcdef\\") at string.c:355
gef➤  n
[... step until interesting stuff ...]
gef➤  p s
$1 = (uschar *) 0x562b1a097790 "abcdef\\"
gef➤  p len
$2 = 0x8
gef➤  p ss
$4 = (uschar *) 0x562b1a097798 ""
gef➤  heap chunks
[... skip uninteresting chunks ...]
Chunk(addr=0x562b1a0975e0, size=0x2020, flags=PREV_INUSE)
    [0x0000562b1a0975e0     00 00 00 00 00 00 00 00 00 20 00 00 00 00 00 00    ......... ......]
Chunk(addr=0x562b1a099600, size=0x1010, flags=PREV_INUSE)
    [0x0000562b1a099600     31 69 37 4a 67 79 2d 30 30 30 32 64 44 2d 50 62    1i7Jgy-0002dD-Pb]
Chunk(addr=0x562b1a09a610, size=0x1fa00, flags=PREV_INUSE)  ←  top chunk

gef➤  grep 1i7Jgy-0002dD-Pb
[+] Searching '1i7Jgy-0002dD-Pb' in memory
[+] In (0x562b1a009000-0x562b1a00d000), permission=rw-
  0x562b1a00abb1 - 0x562b1a00abd6  →   "1i7Jgy-0002dD-Pb (queue run pid 2860)" 
  0x562b1a00ae92 - 0x562b1a00aea2  →   "1i7Jgy-0002dD-Pb" 
[+] In '[heap]'(0x562b1a05a000-0x562b1a0ba000), permission=rw-
  0x562b1a097609 - 0x562b1a097619  →   "1i7Jgy-0002dD-Pb" 
  0x562b1a097641 - 0x562b1a097653  →   "1i7Jgy-0002dD-Pb-H" 
  0x562b1a097663 - 0x562b1a097688  →   "1i7Jgy-0002dD-Pb (queue run pid 2860)" 
  0x562b1a0976a9 - 0x562b1a0976bb  →   "1i7Jgy-0002dD-Pb-D" 
  0x562b1a0976c0 - 0x562b1a0976d2  →   "1i7Jgy-0002dD-Pb-H" 
  0x562b1a0976f1 - 0x562b1a097703  →   "1i7Jgy-0002dD-Pb-H" 
  0x562b1a099600 - 0x562b1a099637  →   "1i7Jgy-0002dD-Pb-H\nDebian-exim 103 114\n<redacted[...]" 
  0x562b1a099c16 - 0x562b1a099c4d  →   "1i7Jgy-0002dD-Pb\n\tfor [email protected]; Mon[...]" 
  0x562b1a099c8d - 0x562b1a099cc4  →   "[email protected]>\n022F From: [email protected][...]" 
[+] In '[stack]'(0x7fff8da2e000-0x7fff8dab0000), permission=rw-
  0x7fff8da65ae9 - 0x7fff8da65afb  →   "1i7Jgy-0002dD-Pb-H" 
  0x7fff8da65bb0 - 0x7fff8da65bc2  →   "1i7Jgy-0002dD-Pb-H" 
  0x7fff8da65eb9 - 0x7fff8da65ecb  →   "1i7Jgy-0002dD-Pb-H"

gef➤  fin
Run till exit from #0  string_unprinting (s=0x5600d6a60790 "abcdef\\") at string.c:366
gef➤  x/16bx 0x5600d6a60798
0x5600d6a60798: 0x61    0x62    0x63    0x64    0x65    0x66    0x00    0x61
0x5600d6a607a0: 0x62    0x63    0x64    0x65    0x66    0x00    0x00    0x00

while (  (len = Ustrlen(big_buffer)) == big_buffer_size-1
    && big_buffer[len-1] != '\n'
    )
    {   /* buffer not big enough for line; certs make this possible */
    uschar * buf;
    if (big_buffer_size >= BIG_BUFFER_SIZE*4) goto SPOOL_READ_ERROR;
    buf = store_get_perm(big_buffer_size *= 2);
    memcpy(buf, big_buffer, --len);
    big_buffer = buf;
    if (Ufgets(big_buffer+len, big_buffer_size-len, f) == NULL)
      goto SPOOL_READ_ERROR;
    }

gef➤  b opendir
Breakpoint 1 at 0x55b87b85e468
gef➤  c
Continuing.
Breakpoint 1, 0x00007f81aebc49a0 in opendir () from target:/lib/x86_64-linux-gnu/libc.so.6
gef➤  p yield_length[0]
$1 = 0x1ff0

gef➤  b closedir
Breakpoint 1 at 0x55dcb4d13898
gef➤  c
Continuing.
Breakpoint 1, 0x00007fb8affcc9f0 in closedir () from target:/lib/x86_64-linux-gnu/libc.so.6
gef➤  fin
Run till exit from #0  0x00007fb8affcc9f0 in closedir () from target:/lib/x86_64-linux-gnu/libc.so.6
gef➤  heap chunks
[... skip uninteresting chunks ...]
Chunk(addr=0x55dcb6d6d5e0, size=0x2020, flags=PREV_INUSE)
    [0x000055dcb6d6d5e0     40 76 d7 b6 dc 55 00 00 00 20 00 00 00 00 00 00    @v...U... ......]
Chunk(addr=0x55dcb6d6f600, size=0x8040, flags=PREV_INUSE)
    [0x000055dcb6d6f600     58 2b 2b b0 b8 7f 00 00 58 2b 2b b0 b8 7f 00 00    X++.....X++.....]
Chunk(addr=0x55dcb6d77640, size=0x2020, flags=)
    [0x000055dcb6d77640     00 00 00 00 00 00 00 00 00 20 00 00 00 00 00 00    ......... ......]
Chunk(addr=0x55dcb6d79660, size=0x1e9b0, flags=PREV_INUSE)  ←  top chunk

gef➤  b string_unprinting
Breakpoint 1 at 0x55d401799540: file string.c, line 355.
gef➤  c
Continuing.
Thread 2.1 "exim4" hit Breakpoint 3, string_unprinting (s=0x55d4039d6990 'a' <repeats 3194 times>, "\\") at string.c:355
gef➤  p yield_length[0]
$1 = 0x1e68

int
spool_read_header(uschar *name, BOOL read_headers, BOOL subdir_set)
{
[... skip uninteresting lines ...]
    else if (Ustrncmp(p, "elo_name", 8) == 0)
      sender_helo_name = string_copy(big_buffer + 11);

/* Check that the message still exists */

message_subdir[0] = f->dir_uschar;
if (Ustat(spool_fname(US"input", message_subdir, f->text, US""), &statbuf) < 0)
  continue;

/* Handle the creation of a randomized list. The first item becomes both
the top and bottom of the list. Subsequent items are inserted either at
the top or the bottom, randomly. This is, I argue, faster than doing a
sort by allocating a random number to each item, and it also saves having
to store the number with each item. */

gef➤  b closedir
Breakpoint 1 at 0x556862b9b898
gef➤  commands
Type commands for breakpoint(s) 1, one per line.
End with a line saying just "end".
>set $ID = ((char *)current_block[0]) + 0x19
>c
>end
gef➤  b queue.c:645 if (int)strcmp(f->text, $ID) == 0
Breakpoint 2 at 0x564f9a43418a: file queue.c, line 647.
gef➤  commands
Type commands for breakpoint(s) 1, one per line.
End with a line saying just "end".
>set follow-fork-mode child
>b string_unprinting
>c
>end
gef➤  c
Continuing.
Thread 2.1 "exim4" hit Breakpoint 1, string_unprinting (s=0x558589a70660 "abcdef\\") at string.c:355
gef➤  heap chunks
[... skip uninteresting chunks ...]
Chunk(addr=0x55ee971d75e0, size=0x2020, flags=PREV_INUSE)
    [0x000055ee971d75e0     40 16 1e 97 ee 55 00 00 00 20 00 00 00 00 00 00    @....U... ......]
Chunk(addr=0x55ee971d9600, size=0x2020, flags=PREV_INUSE)
    [0x000055ee971d9600     30 c6 1d 97 ee 55 00 00 00 20 00 00 00 00 00 00    0....U... ......]
Chunk(addr=0x55ee971db620, size=0x1010, flags=PREV_INUSE)
    [0x000055ee971db620     62 62 62 62 62 62 62 62 62 62 62 62 62 62 62 62    bbbbbbbbbbbbbbbb]
Chunk(addr=0x55ee971dc630, size=0x2ff0, flags=PREV_INUSE)
    [0x000055ee971dc630     20 f6 1d 97 ee 55 00 00 d8 2f 00 00 00 00 00 00     ....U.../......]
Chunk(addr=0x55ee971df620, size=0x2020, flags=PREV_INUSE)
    [0x000055ee971df620     00 00 00 00 00 00 00 00 00 20 00 00 00 00 00 00    ......... ......]
Chunk(addr=0x55ee971e1640, size=0x2020, flags=PREV_INUSE)
    [0x000055ee971e1640     00 96 1d 97 ee 55 00 00 00 20 00 00 00 00 00 00    .....U... ......]
Chunk(addr=0x55ee971e3660, size=0x1e9b0, flags=PREV_INUSE)  ←  top chunk
gef➤ p current_block[0]
$1 = (storeblock *) 0x55ee971df620
gef➤  x/s 0x55ee971e1640 + 0x19
0x55ee971e1659: "16aJgy-baaaad-Pb"

/* Open the message log file if we are using them. This records details of
deliveries, deferments, and failures for the benefit of the mail administrator.
The log is not used by Exim itself to track the progress of a message; that is
done by rewriting the header spool file. */

if (message_logs)
  {
  uschar * fname = spool_fname(US"msglog", message_subdir, id, US"");
  uschar * error;
  int fd;

  if ((fd = open_msglog_file(fname, SPOOL_MODE, &error)) < 0)
    {
    log_write(0, LOG_MAIN|LOG_PANIC, "Couldn't %s message log %s: %s", error,
      fname, strerror(errno));
    return continue_closedown();   /* yields DELIVER_NOT_ATTEMPTED */
    }

  /* Make a C stream out of it. */

  if (!(message_log = fdopen(fd, "a")))
    {
    log_write(0, LOG_MAIN|LOG_PANIC, "Couldn't fdopen message log %s: %s",
      fname, strerror(errno));
    return continue_closedown();   /* yields DELIVER_NOT_ATTEMPTED */
    }
  }

if (!addr->parent)
    deliver_msglog("%s %s: %s%s succeeded\n", now, addr->address,
      driver_name, driver_kind);
  else
    {
    deliver_msglog("%s %s <%s>: %s%s succeeded\n", now, addr->address,
      addr->parent->address, driver_name, driver_kind);
    child_done(addr, now);
    }