Global sieve variables don't work in 2.4.4

Hi everyone!

I have created a minimal reproducible setup. First, let's prepare the environment and create the necessary directories:

getent group vmail >/dev/null \
|| groupadd -g 500 vmail; \
getent passwd vmail \
| awk -F: '$3 == "500" && $4 == "vmail"' >/dev/null \
|| { id vmail >/dev/null 2>&1 && usermod -u 500 -g vmail vmail \
|| useradd -u 500 -g vmail -M -s /usr/sbin/nologin vmail; }

mkdir -p /mail && chown vmail:vmail -R /mail

cat > /mail/global_bug.sieve <<EOF
require ["variables", "include"];
global "global_var";
set "global_var" "hello";
EOF

cat > /mail/before_bug.sieve <<EOF
require ["variables", "include", "vnd.dovecot.debug"];
global "global_var";
include :global :optional "global_bug";
debug_log "\${global_var}";
EOF

Then, we configure dovecot.conf:

dovecot_config_version = 2.4.4
dovecot_storage_version = 2.4.4

auth_allow_cleartext = yes
mail_driver = maildir
mail_home = /mail/%{user}
mail_inbox_path = .INBOX
mail_uid = vmail
mail_gid = vmail
first_valid_uid = 500


protocols {
  imap = yes
}

mail_plugins {
  imap_sieve = yes
}

service imap-login {
  inet_listener imaps {
    port = 0
  }
}

passdb anypass {
  driver = static
  fields {
    nopassword = yes
  }
}

sieve_global_extensions {
  vnd.dovecot.debug = yes
}

sieve_script global_bug {
  driver = file
  path = /mail/global_bug.sieve
  type = global
}

namespace inbox {
  inbox = yes
  separator = /

  mailbox INBOX {
    auto = subscribe

    sieve_script before_bug {
      driver = file
      path = /mail/before_bug.sieve
      cause = APPEND
      type = before
    }
  }
}

If we run an APPEND command to the INBOX directory:

curl -v -u "user1:hello" -k "imap://localhost:143/INBOX" --upload-file /tmp/test.eml

the log shows an empty message.

imap(user1)<3155434><YNISPNZYHtV/AAAB>: sieve: DEBUG:

However, if we change the configuration and the Sieve script by replacing "global" with "personal", I see my hello in debug log:

...
sieve_script global_bug {
  driver = file
  path = /mail/global_bug.sieve
  type = personal # !!!
}
...
require ["variables", "include", "vnd.dovecot.debug"];
global "global_var";
include :personal :optional "global_bug"; # !!!
debug_log "\${global_var}";
...
imap(user1)<3155659><iiiIhNZYgpl/AAAB>: sieve: DEBUG: hello

Why am I unable to import a global variable into a before script if it is defined in a global script?

Thank You in advance!