diff --git a/modoboa_installer/package.py b/modoboa_installer/package.py
index 5354b359..8c4f074e 100644
--- a/modoboa_installer/package.py
+++ b/modoboa_installer/package.py
@@ -29,7 +29,7 @@ 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"
 
@@ -42,6 +42,28 @@ def prepare_system(self):
     def restore_system(self):
         utils.exec_cmd("rm -f {}".format(self.policy_file))
 
+    def add_custom_repository(self,
+                              name: str,
+                              url: str,
+                              key_url: str,
+                              codename: str,
+                              with_source: bool = True):
+        key_file = f"/etc/apt/keyrings/{name}.gpg"
+        utils.exec_cmd(
+            f"wget -O - {key_url} | gpg --dearmor | sudo tee {key_file} > /dev/null"
+        )
+        line_types = ["deb"]
+        if with_source:
+            line_types.append("deb-src")
+        for line_type in line_types:
+            line = (
+                f"{line_type} [arch=amd64 signed-by={key_file}] "
+                f"{url} {codename} main"
+            )
+            target_file = f"/etc/apt/source.list.d/{name}.list"
+            utils.exec_cmd(f'echo "{line} | sude tee {target_file}')
+        self.index_updated = False
+
     def update(self):
         """Update local cache."""
         if self.index_updated:
@@ -82,7 +104,7 @@ class RPMPackage(Package):
 
     def __init__(self, dist_name):
         """Initialize backend."""
-        super(RPMPackage, self).__init__(dist_name)
+        super().__init__(dist_name)
         if "centos" in dist_name:
             self.install("epel-release")
 
diff --git a/modoboa_installer/scripts/rspamd.py b/modoboa_installer/scripts/rspamd.py
index 49af4a83..105f0361 100644
--- a/modoboa_installer/scripts/rspamd.py
+++ b/modoboa_installer/scripts/rspamd.py
@@ -41,17 +41,21 @@ def install_packages(self):
         if debian_based_dist:
             utils.mkdir_safe(
                 "/etc/apt/keyrings",
-                stat.S_IRWXU | stat.S_IRUSR | stat.S_IXUSR,
+                stat.S_IRWXU | stat.S_IRGRP | stat.S_IXGRP |
+                stat.S_IROTH | stat.S_IXOTH,
                 0, 0
             )
 
-            if codename.lower() == "bionic":
+            if codename == "bionic":
                 package.backend.install("software-properties-common")
                 utils.exec_cmd("add-apt-repository ppa:ubuntu-toolchain-r/test")
 
-            utils.exec_cmd("wget -O- https://rspamd.com/apt-stable/gpg.key | gpg --dearmor | sudo tee /etc/apt/keyrings/rspamd.gpg > /dev/null")
-            utils.exec_cmd(f"echo \"deb [arch=amd64 signed-by=/etc/apt/keyrings/rspamd.gpg] http://rspamd.com/apt-stable/ {codename} main\" | sudo tee /etc/apt/sources.list.d/rspamd.list")
-            utils.exec_cmd(f"echo \"deb-src [arch=amd64 signed-by=/etc/apt/keyrings/rspamd.gpg] http://rspamd.com/apt-stable/ {codename} main\"  | sudo tee -a /etc/apt/sources.list.d/rspamd.list")
+            package.backend.add_custom_repository(
+                "rspamd",
+                "http://rspamd.com/apt-stable/",
+                "https://rspamd.com/apt-stable/gpg.key",
+                codename
+            )
             package.backend.update()
 
         return super().install_packages()