diff --git a/nongnu/packages/steam-client.scm b/nongnu/packages/steam-client.scm
index e7592cf..aa5a8c8 100644
--- a/nongnu/packages/steam-client.scm
+++ b/nongnu/packages/steam-client.scm
@@ -120,13 +120,42 @@
      (modify-inputs (package-propagated-inputs libxdamage)
        (replace "libx11" libx11-fixed)))))
 
-(define mesa-fixed
+(define-public mesa-next
   (package
     (inherit mesa)
     (propagated-inputs
      (modify-inputs (package-propagated-inputs mesa)
        (replace "libx11" libx11-fixed)
-       (replace "libxdamage" libxdamage-fixed)))))
+       (replace "libxdamage" libxdamage-fixed)))
+    (name "mesa-next")
+    (version "23.2.1")
+    (source
+     (origin
+       (method url-fetch)
+       (uri (list (string-append "https://archive.mesa3d.org/"
+                                 "mesa-" version ".tar.xz")
+                  (string-append "ftp://ftp.freedesktop.org/pub/mesa/"
+                                 "mesa-" version ".tar.xz")))
+       (sha256
+        (base32
+         "1k61pgw0vcjrlb4299q98cy7iqmk2r7jmb5ika91z01dzhb0dpk4"))))))
+
+(define-public mesa-git
+  (let ((commit "9f4f52f4f3466ba4570f163c869fc1c04b21e5c9")
+        (revision "0"))
+    (package
+      (inherit mesa-next)
+      (name "mesa-git")
+      (version (git-version "23.3.0-devel" revision commit))
+      (source
+       (origin
+         (method git-fetch)
+         (uri (git-reference
+               (url "https://gitlab.freedesktop.org/mesa/mesa")
+               (commit commit)))
+         (file-name (git-file-name name version))
+         (sha256
+          (base32 "17s2kyf0dsmvi7cnvrmsy39db6j9sba94y34345kqmg4rc2z150a")))))))
 
 (define steam-client-libs
   `(("bash" ,bash)                      ; Required for steam startup.
@@ -151,9 +180,7 @@
     ("libvdpau-va-gl" ,libvdpau-va-gl)  ; Additional VDPAU support.
     ("llvm" ,llvm-for-mesa)             ; Required for mesa.
     ("lsof" ,lsof)                      ; Required for some friend's list actions.
-    ;; TODO: Set back to mesa once libx11 is ungrafted upstream or once
-    ;; <https://issues.guix.gnu.org/53406> is fixed.
-    ("mesa" ,mesa-fixed)                ; Required for steam startup.
+    ("mesa" ,mesa-next)                  ; Required for steam startup.
     ("nss-certs" ,nss-certs)            ; Required for steam login.
     ("pciutils" ,pciutils)              ; Tries to run lspci at steam startup.
     ("procps" ,procps)
diff --git a/nonguix/multiarch-container.scm b/nonguix/multiarch-container.scm
index b333b71..e9243f0 100644
--- a/nonguix/multiarch-container.scm
+++ b/nonguix/multiarch-container.scm
@@ -330,6 +330,9 @@ in a sandboxed FHS environment."
                        ,@(exists-> (getenv "XAUTHORITY"))
                        #$@(ngc-shared container)))
               (DEBUG (equal? (getenv "DEBUG") "1"))
+              (extra-shares (if (getenv "GUIX_SANDBOX_EXTRA_SHARES")
+                                (string-split (getenv "GUIX_SANDBOX_EXTRA_SHARES") #\:)
+                                #f))
               (args (cdr (command-line)))
               (command (if DEBUG '()
                            `("--" ,run ,@args))))
@@ -362,7 +365,9 @@ in a sandboxed FHS environment."
                   ,@(map add-path expose)
                   ,@(map (lambda (item)
                            (add-path item #:writable? #t))
-                         share)
+                         (if extra-shares
+                             (append share extra-shares)
+                             share))
                   "-m" ,manifest-file
                   ,@command))))))