diff --git a/modoboa_installer/package.py b/modoboa_installer/package.py
index e1b9bf7..21aa6f8 100644
--- a/modoboa_installer/package.py
+++ b/modoboa_installer/package.py
@@ -5,7 +5,7 @@ import re
 from . import utils
 
 
-class Package(object):
+class Package:
     """Base classe."""
 
     def __init__(self, dist_name):
@@ -29,10 +29,16 @@ class DEBPackage(Package):
     FORMAT = "deb"
 
     def __init__(self, dist_name):
-        super(DEBPackage, self).__init__(dist_name)
+        super().__init__(dist_name)
         self.index_updated = False
         self.policy_file = "/usr/sbin/policy-rc.d"
 
+    def enable_backports(self, codename):
+        code, output = utils.exec_cmd(f"grep {codename}-backports /etc/apt/sources.list")
+        if code:
+            with open(f"/etc/apt/sources.list.d/backports.list", "w") as fp:
+                fp.write(f"deb http://deb.debian.org/debian {codename}-backports main\n")
+
     def prepare_system(self):
         """Make sure services don't start at installation."""
         with open(self.policy_file, "w") as fp:
diff --git a/modoboa_installer/scripts/dovecot.py b/modoboa_installer/scripts/dovecot.py
index 30fb180..2559b70 100644
--- a/modoboa_installer/scripts/dovecot.py
+++ b/modoboa_installer/scripts/dovecot.py
@@ -55,10 +55,19 @@ class Dovecot(base.Installer):
         if package.backend.FORMAT == "deb":
             if "pop3" in self.config.get("dovecot", "extra_protocols"):
                 packages += ["dovecot-pop3d"]
-        return super().get_packages() + packages
+        packages += super().get_packages()
+        backports_codename = getattr(self, "backports_codename", None)
+        if backports_codename:
+            packages = [f"{package}/{backports_codename}-backports" for package in packages]
+        return packages
 
     def install_packages(self):
         """Preconfigure Dovecot if needed."""
+        name, version = utils.dist_info()
+        name = name.lower()
+        if name.startswith("debian") and version.startswith("12"):
+            package.backend.enable_backports("bookworm")
+            self.backports_codename = "bookworm"
         package.backend.preconfigure(
             "dovecot-core", "create-ssl-cert", "boolean", "false")
         super().install_packages()
diff --git a/modoboa_installer/scripts/postfix.py b/modoboa_installer/scripts/postfix.py
index beba9f2..6a2d743 100644
--- a/modoboa_installer/scripts/postfix.py
+++ b/modoboa_installer/scripts/postfix.py
@@ -29,7 +29,7 @@ class Postfix(base.Installer):
             packages = ["postfix-{}".format(self.db_driver)]
         else:
             packages = []
-        return super(Postfix, self).get_packages() + packages
+        return super().get_packages() + packages
 
     def install_packages(self):
         """Preconfigure postfix package installation."""
@@ -46,7 +46,7 @@ class Postfix(base.Installer):
 
         package.backend.preconfigure(
             "postfix", "main_mailer_type", "select", "No configuration")
-        super(Postfix, self).install_packages()
+        super().install_packages()
 
     def get_template_context(self):
         """Additional variables."""