diff --git a/perl-5.33.5-Use-perl.h-versions-of-PERL_UNUSED_foo-in-XSUB.h.patch b/perl-5.33.5-Use-perl.h-versions-of-PERL_UNUSED_foo-in-XSUB.h.patch
new file mode 100644
index 0000000..31d7bf4
--- /dev/null
+++ b/perl-5.33.5-Use-perl.h-versions-of-PERL_UNUSED_foo-in-XSUB.h.patch
@@ -0,0 +1,43 @@
+From 036189b0a003875df7bf09c7f7fd702267f549e5 Mon Sep 17 00:00:00 2001
+From: Karl Williamson <khw@cpan.org>
+Date: Sat, 26 Dec 2020 08:44:08 -0700
+Subject: [PATCH] Use perl.h versions of PERL_UNUSED_foo in XSUB.h
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+This commit was applied to perl.h, but not to XSUB.h:
+
+commit a730e3f230f364cffe49370f816f975ae7c9c403
+Author: Jarkko Hietaniemi <jhi@iki.fi>
+Date:   Thu Sep 4 09:08:33 2014 -0400
+
+Use sizeof() in UNUSED_ARG and UNUSED_VAR to avoid accessing the values.
+
+The values might even be uninitialized in the case of PERL_UNUSED_VAR.
+
+Signed-off-by: Petr Písař <ppisar@redhat.com>
+---
+ XSUB.h | 4 ++--
+ 1 file changed, 2 insertions(+), 2 deletions(-)
+
+diff --git a/XSUB.h b/XSUB.h
+index 616d813840..c1e3959885 100644
+--- a/XSUB.h
++++ b/XSUB.h
+@@ -108,10 +108,10 @@ is a lexical C<$_> in scope.
+ */
+ 
+ #ifndef PERL_UNUSED_ARG
+-#  define PERL_UNUSED_ARG(x) ((void)x)
++#  define PERL_UNUSED_ARG(x) ((void)sizeof(x))
+ #endif
+ #ifndef PERL_UNUSED_VAR
+-#  define PERL_UNUSED_VAR(x) ((void)x)
++#  define PERL_UNUSED_VAR(x) ((void)sizeof(x))
+ #endif
+ 
+ #define ST(off) PL_stack_base[ax + (off)]
+-- 
+2.26.2
+
diff --git a/perl.spec b/perl.spec
index 35fc75a..a64d4b9 100644
--- a/perl.spec
+++ b/perl.spec
@@ -255,6 +255,9 @@ Patch50:        perl-5.33.5-Fix-buggy-fc-in-Turkish-locale.patch
 # in upstream after 5.33.5
 Patch51:        perl-5.33.5-op.c-croak-on-my-_-when-use-utf8-is-in-effect.patch
 
+# Fix PERL_UNUSED_ARG() definition in XSUB.h, in upstream after 5.33.5
+Patch52:        perl-5.33.5-Use-perl.h-versions-of-PERL_UNUSED_foo-in-XSUB.h.patch
+
 # Link XS modules to libperl.so with EU::CBuilder on Linux, bug #960048
 Patch200:       perl-5.16.3-Link-XS-modules-to-libperl.so-with-EU-CBuilder-on-Li.patch
 
@@ -4307,6 +4310,7 @@ you're not running VMS, this module does nothing.
 %patch49 -p1
 %patch50 -p1
 %patch51 -p1
+%patch52 -p1
 %patch200 -p1
 %patch201 -p1
 
@@ -4357,6 +4361,7 @@ perl -x patchlevel.h \
     'Fedora Patch49: Use duplocale() if available' \
     'Fedora Patch50: Fix fc() in Turkish locale' \
     'Fedora Patch51: Fix croaking on "my $_" when "use utf8" is in effect (GH#18449)' \
+    'Fedora Patch52: Fix PERL_UNUSED_ARG() definition in XSUB.h' \
     'Fedora Patch200: Link XS modules to libperl.so with EU::CBuilder on Linux' \
     'Fedora Patch201: Link XS modules to libperl.so with EU::MM on Linux' \
     %{nil}
@@ -7089,6 +7094,7 @@ popd
 - Use duplocale() if available
 - Fix fc() in Turkish locale
 - Fix croaking on "my $_" when "use utf8" is in effect (GH#18449)
+- Fix PERL_UNUSED_ARG() definition in XSUB.h
 
 * Tue Jan 26 2021 Fedora Release Engineering <releng@fedoraproject.org> - 4:5.32.1-470
 - Rebuilt for https://fedoraproject.org/wiki/Fedora_34_Mass_Rebuild