diff --git a/lib/HTTP/Cookies/Netscape.pm b/lib/HTTP/Cookies/Netscape.pm
index 34055e26..07d6eecb 100644
--- a/lib/HTTP/Cookies/Netscape.pm
+++ b/lib/HTTP/Cookies/Netscape.pm
@@ -30,9 +30,14 @@ sub load {
         my ( $domain, $bool1, $path, $secure, $expires, $key, $val )
             = split( /\t/, $line );
         $secure = ( $secure eq "TRUE" );
+
+        # An expiry of 0 means a session cookie (no expiration), per the
+        # curl/cookies.txt convention. Pass undef max-age so set_cookie() keeps
+        # it instead of reading 0-$now as an already-expired cookie.
+        my $maxage = $expires ? $expires - $now : undef;
         $self->set_cookie(
-            undef,   $key,            $val, $path, $domain, undef, 0,
-            $secure, $expires - $now, 0
+            undef,   $key,    $val, $path, $domain, undef, 0,
+            $secure, $maxage, 0
         );
     }
     1;
@@ -64,11 +69,19 @@ EOT
         sub {
             my (
                 $version, $key,     $val, $path, $domain, $port, $path_spec,
-                $secure,  $expires, $discard, $rest
+                $secure,  $expires, $discard
             ) = @_;
             return if $discard && !$args{'ignore_discard'};
-            $expires = $expires ? $expires - $HTTP::Cookies::EPOCH_OFFSET : 0;
-            return if $now > $expires;
+
+            # A session cookie (no expiry) is written with an expiry of 0 and kept,
+            # matching curl. Only drop a cookie that has a real, past expiry.
+            if ($expires) {
+                $expires = $expires - $HTTP::Cookies::EPOCH_OFFSET;
+                return if $now > $expires;
+            }
+            else {
+                $expires = 0;
+            }
             $secure = $secure ? "TRUE" : "FALSE";
             my $bool = $domain =~ /^\./ ? "TRUE" : "FALSE";
             print {$fh} join(
diff --git a/t/cookies.t b/t/cookies.t
index 4c23beab..723b0276 100644
--- a/t/cookies.t
+++ b/t/cookies.t
@@ -5,7 +5,7 @@ use HTTP::Request  ();
 use HTTP::Response ();
 use URI            ();
 
-use Test::More tests => 79;
+use Test::More tests => 80;
 
 #-------------------------------------------------------------------
 # First we check that it works for the original example at
@@ -453,9 +453,13 @@ $c->save;
 undef($c);
 
 $c = HTTP::Cookies::Netscape->new( file => $file );
-is( count_cookies($c), 1 );    # 2 of them discarded on save
+
+# foo2 (Discard) dropped on save; foo1 (max-age) and foo3 (session cookie,
+# no expiry) are kept, matching curl
+is( count_cookies($c), 2 );
 
 like( $c->as_string, qr/foo1=bar/ );
+like( $c->as_string, qr/foo3=bar/ );    # session cookie survives save/load
 undef($c);
 unlink($file);
 
diff --git a/t/netscape.t b/t/netscape.t
new file mode 100644
index 00000000..5741cea3
--- /dev/null
+++ b/t/netscape.t
@@ -0,0 +1,92 @@
+#!perl -w
+
+# Session cookies (no expiry) must round-trip through the Netscape/cookies.txt
+# format the same way curl and yt-dlp treat them: written with an expiry of 0,
+# and read back as a session cookie (not as an ancient/expired cookie).
+
+use strict;
+use warnings;
+
+use Test::More tests => 6;
+
+use File::Temp qw(tempdir);
+use File::Spec ();
+
+use HTTP::Cookies::Netscape;
+
+my $dir  = tempdir( CLEANUP => 1 );
+my $file = File::Spec->catfile( $dir, 'cookies.txt' );
+
+sub cookie_names {
+    my $jar = shift;
+    my %names;
+    $jar->scan( sub { $names{ $_[1] } = 1 } );
+    return \%names;
+}
+
+# A session cookie has no Max-Age/Expires, so set_cookie() gets an undef maxage.
+my $jar = HTTP::Cookies::Netscape->new;
+$jar->set_cookie(
+    undef, 'sessionid', 'abc123', '/', '.example.com', undef,
+    0,     0,           undef,    0
+);
+
+# A normal persistent cookie, far in the future.
+$jar->set_cookie(
+    undef, 'persistent', 'xyz789',             '/', '.example.com', undef,
+    0,     0,            10 * 365 * 24 * 3600, 0
+);
+
+is_deeply(
+    cookie_names($jar), { sessionid => 1, persistent => 1 },
+    'jar holds both cookies before saving'
+);
+
+$jar->save($file);
+
+my $content = do {
+    open my $fh, '<', $file or die "open $file: $!";
+    local $/;
+    <$fh>;
+};
+
+like(
+    $content,
+    qr/^\.example\.com\t.*\t0\tsessionid\tabc123$/m,
+    'session cookie is written with an expiry of 0 (curl convention)'
+);
+like(
+    $content,
+    qr/\tpersistent\txyz789$/m,
+    'persistent cookie is written'
+);
+
+my $loaded = HTTP::Cookies::Netscape->new( file => $file );
+
+ok(
+    cookie_names($loaded)->{sessionid},
+    'session cookie survives a save/load round-trip'
+);
+ok(
+    cookie_names($loaded)->{persistent},
+    'persistent cookie survives a save/load round-trip'
+);
+
+# Regression guard: a cookie whose expiry is already in the past must NOT be
+# saved. (maxage of 1s, then we doctor the stored expiry into the past.)
+my $expired = HTTP::Cookies::Netscape->new;
+$expired->set_cookie(
+    undef, 'stale', 'old', '/', '.example.com', undef,
+    0,     0,       1,     0
+);
+$expired->scan( sub { } );    # no-op, keeps API parallel
+
+# Force the stored absolute expiry into the past.
+$expired->{COOKIES}{'.example.com'}{'/'}{stale}[5] = time - 3600;
+my $expfile = File::Spec->catfile( $dir, 'expired.txt' );
+$expired->save($expfile);
+my $expired_loaded = HTTP::Cookies::Netscape->new( file => $expfile );
+ok(
+    !cookie_names($expired_loaded)->{stale},
+    'already-expired cookie is not saved'
+);