diff --git a/nixos/modules/misc/version.nix b/nixos/modules/misc/version.nix
index b3cdaf5568d4..1067b21a22b0 100644
--- a/nixos/modules/misc/version.nix
+++ b/nixos/modules/misc/version.nix
@@ -89,6 +89,12 @@ in
 
     stateVersion = mkOption {
       type = types.str;
+      # TODO Remove this and drop the default of the option so people are forced to set it.
+      # Doing this also means fixing the comment in nixos/modules/testing/test-instrumentation.nix
+      apply = v:
+        lib.warnIf (options.system.stateVersion.highestPrio == (lib.mkOptionDefault { }).priority)
+          "system.stateVersion is not set, defaulting to ${v}. Read why this matters on https://nixos.org/manual/nixos/stable/options.html#opt-system.stateVersion."
+          v;
       default = cfg.release;
       defaultText = literalExpression "config.${opt.release}";
       description = lib.mdDoc ''
@@ -149,14 +155,6 @@ in
       "os-release".text = attrsToText osReleaseContents;
     };
 
-    # We have to use `warnings` because when warning in the default of the option
-    # the warning would also be shown when building the manual since the manual
-    # has to evaluate the default.
-    #
-    # TODO Remove this and drop the default of the option so people are forced to set it.
-    # Doing this also means fixing the comment in nixos/modules/testing/test-instrumentation.nix
-    warnings = lib.optional (options.system.stateVersion.highestPrio == (lib.mkOptionDefault { }).priority)
-      "system.stateVersion is not set, defaulting to ${config.system.stateVersion}. Read why this matters on https://nixos.org/manual/nixos/stable/options.html#opt-system.stateVersion.";
   };
 
   # uses version info nixpkgs, which requires a full nixpkgs path
diff --git a/nixos/modules/services/matrix/synapse.nix b/nixos/modules/services/matrix/synapse.nix
index b9b581acb34a..3087d879b9d2 100644
--- a/nixos/modules/services/matrix/synapse.nix
+++ b/nixos/modules/services/matrix/synapse.nix
@@ -507,6 +507,12 @@ in {
                 sqlite3 = null;
                 psycopg2 = "matrix-synapse";
               }.${cfg.settings.database.name};
+              defaultText = lib.literalExpression ''
+                {
+                  sqlite3 = null;
+                  psycopg2 = "matrix-synapse";
+                }.''${cfg.settings.database.name};
+              '';
               description = lib.mdDoc ''
                 Username to connect with psycopg2, set to null
                 when using sqlite3.