diff --git a/perlio.c b/perlio.c
index 8d0ee5c23a45..5df638b058cd 100644
--- a/perlio.c
+++ b/perlio.c
@@ -1265,14 +1265,14 @@ PerlIOScalar_write(pTHX_ PerlIO * f, const void *vbuf, Size_t count)
 	    SETERRNO(EINVAL, SS_IVCHAN);
 	    return 0;
 	}
+        /* Avoid calling SvCUR() on undef'ed SVs */
+        STRLEN const cur = SvOK(sv) ? SvCUR(sv) : 0;
 	if ((PerlIOBase(f)->flags) & PERLIO_F_APPEND) {
-	    dst = SvGROW(sv, SvCUR(sv) + count + 1);
+	    dst = SvGROW(sv, cur + count + 1);
 	    offset = SvCUR(sv);
 	    s->posn = offset + count;
 	}
 	else {
-	    STRLEN const cur = SvCUR(sv);
-
             /* ensure we don't try to create ridiculously large
              * SVs on small platforms
              */
diff --git a/pod/perldelta.pod b/pod/perldelta.pod
index 412acc5b0134..fb62a2613447 100644
--- a/pod/perldelta.pod
+++ b/pod/perldelta.pod
@@ -374,6 +374,12 @@ used to be parsed incorrectly.
 
 =item *
 
+When a scalar variable used as the target of a filehandle is C<undef>'ed
+while being output, garbage bytes would be left in that scalar.
+[L<GH #24008|https://github.com/Perl/perl5/issues/24008>]
+
+=item *
+
 XXX
 
 =back
diff --git a/t/io/scalar.t b/t/io/scalar.t
index ca854b44c245..01fe7595b034 100644
--- a/t/io/scalar.t
+++ b/t/io/scalar.t
@@ -12,7 +12,7 @@ use strict;
 use Fcntl qw(SEEK_SET SEEK_CUR SEEK_END); # Not 0, 1, 2 everywhere.
 use Errno qw(EACCES);
 
-plan(128);
+plan(129);
 
 my $fh;
 my $var = "aaa\n";
@@ -528,3 +528,11 @@ SKIP:
     select((select($fh), ++$|)[0]);
     ok(!(print $fh "x"), "write to a large offset");
 }
+
+{ # GH #24008
+    open my $fh, '>', \my $str or die $!;
+    print $fh "xxxxx";
+    undef $str;
+    print $fh "y";
+    is($str, "\0\0\0\0\0y", "write to undef'ed variable");
+}