diff --git a/src/doc/shldata-rw.h/shldata_write.3.md b/src/doc/shldata-rw.h/shldata_write.3.md
index c7ce352..b125016 100644
--- a/src/doc/shldata-rw.h/shldata_write.3.md
+++ b/src/doc/shldata-rw.h/shldata_write.3.md
@@ -56,6 +56,13 @@ If the magic is valid, parameters will read and the encrypted data will then be
 decrypted using the password pointed by `pwd` of length `plen` and placed into
 the *stralloc* pointed by `sa`.
 
+! INFO:
+! It is possible to set the value pointed to be `magic` to the expected magic
+! from the file. `shldata_read`() will check the value before reading the file,
+! and if it was set to a valid magic (as per `shldata_chkmagic`()) instead of
+! just checking the magic from the file is valid, it will check that it matches
+! the expected value.
+
 # RETURN VALUE
 
 The `shldata_chkmagic`() function returns 1 is `magic` is a valid shielded data
@@ -70,7 +77,7 @@ The `shldata_write`() and `shldta_read`() functions may fail if :
 
 : *EINVAL*
 :: The magic number (given in `magic` or read from `file`, respectively) isn't
-:: a valid magic for a shielded data file.
+:: a valid magic for a shielded data file (or doesn't match the expected magic).
 
 : *ENOMEM*
 :: Out of memory.
diff --git a/src/liblimb/shldata-rw.h/shldata_read.c b/src/liblimb/shldata-rw.h/shldata_read.c
index 043d177..ab86ed6 100644
--- a/src/liblimb/shldata-rw.h/shldata_read.c
+++ b/src/liblimb/shldata-rw.h/shldata_read.c
@@ -1,12 +1,22 @@
 /* This file is part of limb                           https://lila.oss/limb
  * Copyright (C) 2023 Olivier Brunel                          jjk@jjacky.com */
 /* SPDX-License-Identifier: GPL-2.0-only */
+#include <errno.h>
 #include <limb/buffer.h>
 #include <limb/buffer-shldata.h>
 #include <limb/djbunix.h>
 #include <limb/shldata-rw.h>
 #include <limb/unix-transactional.h>
 
+static int
+chkmagic(u32 magic, u32 wmagic)
+{
+    if (!wmagic) return shldata_chkmagic(magic);
+    if (magic == wmagic) return 1;
+
+    return (errno = EINVAL, 0);
+}
+
 int
 shldata_read(u32 *magic, u64 *ver, stralloc *sa, int bfd, const char *file,
              const char *pwd, size_t plen)
@@ -20,9 +30,12 @@ shldata_read(u32 *magic, u64 *ver, stralloc *sa, int bfd, const char *file,
 
     buffer_shldata_ctx bsd = BUFFER_SHLDATA_ZERO;
 
+    u32 wmagic;
+    wmagic = (shldata_chkmagic(*magic)) ? *magic : 0;
+
     size_t salen = sa->len;
     if (!buffer_gethdr(&b, magic, ver)
-            || !shldata_chkmagic(*magic)
+            || !chkmagic(*magic, wmagic)
             || !buffer_shldata_getinit_sa(&b, pwd, plen, sa, &bsd)
             || !stralloc_readyplus(sa, buffer_shldata_datasize(&bsd))
             || !buffer_shldata_get(&b, sa->s + sa->len, buffer_shldata_datasize(&bsd), &bsd)