diff --git a/nixos/modules/services/matrix/synapse.nix b/nixos/modules/services/matrix/synapse.nix
index 34930a7ba69b3..e627c34cfac41 100644
--- a/nixos/modules/services/matrix/synapse.nix
+++ b/nixos/modules/services/matrix/synapse.nix
@@ -12,7 +12,9 @@ let
 
   usePostgresql = cfg.settings.database.name == "psycopg2";
   hasLocalPostgresDB = let args = cfg.settings.database.args; in
-    usePostgresql && (!(args ? host) || (elem args.host [ "localhost" "127.0.0.1" "::1" ]));
+    usePostgresql
+    && (!(args ? host) || (elem args.host [ "localhost" "127.0.0.1" "::1" ]))
+    && config.services.postgresql.enable;
   hasWorkers = cfg.workers != { };
 
   listenerSupportsResource = resource: listener:
@@ -944,23 +946,6 @@ in {
           by synapse in `services.matrix-synapse.settings.listeners` or in one of the workers!
         '';
       }
-      {
-        assertion = hasLocalPostgresDB -> config.services.postgresql.enable;
-        message = ''
-          Cannot deploy matrix-synapse with a configuration for a local postgresql database
-            and a missing postgresql service. Since 20.03 it's mandatory to manually configure the
-            database (please read the thread in https://github.com/NixOS/nixpkgs/pull/80447 for
-            further reference).
-
-            If you
-            - try to deploy a fresh synapse, you need to configure the database yourself. An example
-              for this can be found in <nixpkgs/nixos/tests/matrix/synapse.nix>
-            - update your existing matrix-synapse instance, you simply need to add `services.postgresql.enable = true`
-              to your configuration.
-
-          For further information about this update, please read the release-notes of 20.03 carefully.
-        '';
-      }
       {
         assertion = hasWorkers -> cfg.settings.redis.enabled;
         message = ''
@@ -1034,9 +1019,11 @@ in {
             partOf = [ "matrix-synapse.target" ];
             wantedBy = [ "matrix-synapse.target" ];
             unitConfig.ReloadPropagatedFrom = "matrix-synapse.target";
+            requires = optional hasLocalPostgresDB "postgresql.service";
           }
           else {
             after = [ "network-online.target" ] ++ optional hasLocalPostgresDB "postgresql.service";
+            requires = optional hasLocalPostgresDB "postgresql.service";
             wantedBy = [ "multi-user.target" ];
           };
         baseServiceConfig = {