diff --git a/ext/XS-APItest/APItest.xs b/ext/XS-APItest/APItest.xs
index 455bdf67d632..1676ded76c8d 100644
--- a/ext/XS-APItest/APItest.xs
+++ b/ext/XS-APItest/APItest.xs
@@ -4941,7 +4941,11 @@ rc_add(sv1, sv2)
         rpp_replace_2_1(r);
         return;
 
-
+void
+modify_pv(IV pi, IV sz)
+    PPCODE:
+        /* used by op/pack.t when testing pack "p" */
+        memset(INT2PTR(char *, pi), 'y', sz);
 
 MODULE = XS::APItest PACKAGE = XS::APItest::AUTOLOADtest
 
diff --git a/pp_pack.c b/pp_pack.c
index f436b45d2bb7..bb3304b13383 100644
--- a/pp_pack.c
+++ b/pp_pack.c
@@ -3076,7 +3076,7 @@ S_pack_rec(pTHX_ SV *cat, tempsym_t* symptr, SV **beglist, SV **endlist )
                         Perl_ck_warner(aTHX_ packWARN(WARN_PACK),
                                        "Attempt to pack pointer to temporary value");
                     }
-                    if (SvPOK(fromstr) || SvNIOK(fromstr))
+                    if (SvREADONLY(fromstr))
                         aptr = SvPV_nomg_const_nolen(fromstr);
                     else
                         aptr = SvPV_force_flags_nolen(fromstr, 0);
diff --git a/t/op/pack.t b/t/op/pack.t
index 93865b0b3d5f..441a2c01841b 100644
--- a/t/op/pack.t
+++ b/t/op/pack.t
@@ -6,7 +6,7 @@ BEGIN {
     set_up_inc(qw '../lib ../cpan/Math-BigInt/lib');
 }
 
-plan tests => 14722;
+plan tests => 14724;
 
 use strict;
 use warnings qw(FATAL all);
@@ -343,6 +343,20 @@ sub foo { my $a = "a"; return $a . $a++ . $a++ }
   like($warning, qr/temporary val/);
 }
 
+SKIP:
+{
+    # based on https://github.com/Perl/perl5/issues/22380
+    eval { require XS::APItest; 1 }
+      or skip "Cannot load XS::APItest", 2;
+    # writable "P"
+    my $orig = "x" x 36;
+    my $data = $orig;
+    my $ptr = unpack 'j', pack 'P', $data;
+    XS::APItest::modify_pv($ptr, length $data);
+    is($data, "y" x 36, "check \$data was modified");
+    is($orig, "x" x 36, "check \$orig wasn't modified");
+}
+
 # undef should give null pointer
 like(pack("p", undef), qr/^\0+$/);
 like(pack("p<", undef), qr/^\0+$/);