diff --git a/nixos/modules/services/misc/nixos-manual.nix b/nixos/modules/services/misc/nixos-manual.nix
index 023a933fd893..7202269d3421 100644
--- a/nixos/modules/services/misc/nixos-manual.nix
+++ b/nixos/modules/services/misc/nixos-manual.nix
@@ -6,7 +6,10 @@
 
 with lib;
 
-let cfg = config.services.nixosManual; in
+let
+  cfg = config.services.nixosManual;
+  cfgd = config.documentation;
+in
 
 {
 
@@ -44,7 +47,7 @@ let cfg = config.services.nixosManual; in
   config = mkIf cfg.showManual {
 
     assertions = [{
-      assertion = config.documentation.nixos.enable;
+      assertion = cfgd.enable && cfgd.nixos.enable;
       message   = "Can't enable `service.nixosManual.showManual` without `documentation.nixos.enable`";
     }];