diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index f4c005a9a..3be797d21 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -492,6 +492,21 @@ cross-mingw64:
       - _build/gthread/libgthread-2.0-0.dll
       - _build/gobject/libgobject-2.0-0.dll
 
+# A note about msys2: it’s a rolling release distribution, running Windows under
+# Docker isn’t really supported, and the win32-ps CI runner is shared. All that
+# adds up to mean that we have to run CI against the latest msys2 packages, and
+# that this occasionally causes build failures in GLib due to changes in msys2.
+# In order to avoid that pre-empting other GLib development, the policy in such
+# cases is to:
+#  1. Immediately and without hesitation make the msys2-* CI jobs non-fatal
+#     (add `allow_failure: true` below).
+#  2. File an issue about fixing the GLib msys2 build and re-enabling failure
+#     on the CI job
+#  3. Set the milestone for that issue to be the next GLib release, so it’s done
+#     in a timely manner; and tag it as ~win32 so the GLib Windows maintainers
+#     are notified and can work on it.
+#  4. Rebase any pending broken MRs on top of the commit which makes the CI job
+#     non-fatal, so that development on `main` is unblocked.
 msys2-mingw32:
   extends: .only-default-and-merges
   stage: build
@@ -520,6 +535,7 @@ msys2-mingw32:
       - _coverage/
       - _reference/
 
+# See the note about msys2 CI job failure policy above.
 msys2-clang64:
   extends: .only-schedules-or-manual
   stage: build
diff --git a/docs/supported-platforms.md b/docs/supported-platforms.md
index 74dd01d1a..f883f74b2 100644
--- a/docs/supported-platforms.md
+++ b/docs/supported-platforms.md
@@ -41,7 +41,7 @@ GLib is regularly built on at least the following systems:
    - Fedora (34, https://gitlab.gnome.org/GNOME/glib/-/blob/main/.gitlab-ci/fedora.Dockerfile)
    - Debian (Bullseye, https://gitlab.gnome.org/GNOME/glib/-/blob/main/.gitlab-ci/debian-stable.Dockerfile)
    - Windows (MinGW64)
-   - Windows (msys2-mingw32)
+   - Windows (msys2-mingw32 and msys2-clang64; msys2 is a rolling release distribution)
    - Windows (Visual Studio 2017, and a static linking version)
    - Android (NDK r23b, API 31, arm64, https://gitlab.gnome.org/GNOME/glib/-/blob/main/.gitlab-ci/android-ndk.sh)
    - FreeBSD (12 and 13)
diff --git a/glib/gnulib/vasnprintf.c b/glib/gnulib/vasnprintf.c
index a5b68db8c..7e151b462 100644
--- a/glib/gnulib/vasnprintf.c
+++ b/glib/gnulib/vasnprintf.c
@@ -379,7 +379,7 @@ multiply (mpn_t src1, mpn_t src2, mpn_t *dest)
     {
       /* src1 or src2 is zero.  */
       dest->nlimbs = 0;
-      dest->limbs = (mp_limb_t *) malloc (1);
+      dest->limbs = (mp_limb_t *) malloc (sizeof (mp_limb_t));
     }
   else
     {
diff --git a/glib/tests/atomic.c b/glib/tests/atomic.c
index 9d57d2114..82c5c9e14 100644
--- a/glib/tests/atomic.c
+++ b/glib/tests/atomic.c
@@ -136,6 +136,7 @@ test_types (void)
    * to make sure that we don’t warn when built against older third party code. */
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wincompatible-pointer-types"
+#pragma GCC diagnostic ignored "-Wdiscarded-qualifiers"
   g_atomic_pointer_set (&vp_str_vol, NULL);
   g_atomic_pointer_set (&vp_str, str);
   res = g_atomic_pointer_compare_and_exchange (&vp_str_vol, NULL, str);
diff --git a/glib/tests/mem-overflow.c b/glib/tests/mem-overflow.c
index f19534102..b8b65c17a 100644
--- a/glib/tests/mem-overflow.c
+++ b/glib/tests/mem-overflow.c
@@ -71,11 +71,11 @@ MEM_OVERFLOW_TEST (new0_b, p = g_new0 (X, b))
 MEM_OVERFLOW_TEST (renew_a, p = g_malloc (1); p = g_renew (X, p, a))
 MEM_OVERFLOW_TEST (renew_b, p = g_malloc (1); p = g_renew (X, p, b))
 
-MEM_OVERFLOW_TEST_FULL (aligned_alloc_a, p = g_aligned_alloc (sizeof(X), a, 16), g_aligned_free)
-MEM_OVERFLOW_TEST_FULL (aligned_alloc_b, p = g_aligned_alloc (sizeof(X), b, 16), g_aligned_free)
+MEM_OVERFLOW_TEST_FULL (aligned_alloc_a, p = g_aligned_alloc (a, sizeof(X), 16), g_aligned_free)
+MEM_OVERFLOW_TEST_FULL (aligned_alloc_b, p = g_aligned_alloc (b, sizeof(X), 16), g_aligned_free)
 
-MEM_OVERFLOW_TEST_FULL (aligned_alloc0_a, p = g_aligned_alloc0 (sizeof(X), a, 16), g_aligned_free)
-MEM_OVERFLOW_TEST_FULL (aligned_alloc0_b, p = g_aligned_alloc0 (sizeof(X), b, 16), g_aligned_free)
+MEM_OVERFLOW_TEST_FULL (aligned_alloc0_a, p = g_aligned_alloc0 (a, sizeof(X), 16), g_aligned_free)
+MEM_OVERFLOW_TEST_FULL (aligned_alloc0_b, p = g_aligned_alloc0 (b, sizeof(X), 16), g_aligned_free)
 
 static void
 mem_overflow_malloc_0 (void)