diff --git a/nixos/modules/misc/documentation.nix b/nixos/modules/misc/documentation.nix
index bc43cc33b5d..fe0263f158f 100644
--- a/nixos/modules/misc/documentation.nix
+++ b/nixos/modules/misc/documentation.nix
@@ -217,7 +217,7 @@ in
           manualCache = pkgs.runCommandLocal "man-cache" { }
           ''
             echo "MANDB_MAP ${manualPages}/share/man $out" > man.conf
-            ${pkgs.man-db}/bin/mandb -C man.conf -psc
+            ${pkgs.man-db}/bin/mandb -C man.conf -psc >/dev/null 2>&1
           '';
         in
         ''
diff --git a/nixos/modules/programs/fish.nix b/nixos/modules/programs/fish.nix
index 39b92edf2ac..50d1077dd41 100644
--- a/nixos/modules/programs/fish.nix
+++ b/nixos/modules/programs/fish.nix
@@ -103,7 +103,7 @@ in
     programs.fish.shellAliases = mapAttrs (name: mkDefault) cfge.shellAliases;
 
     # Required for man completions
-    documentation.man.generateCaches = true;
+    documentation.man.generateCaches = lib.mkDefault true;
 
     environment.etc."fish/foreign-env/shellInit".text = cfge.shellInit;
     environment.etc."fish/foreign-env/loginShellInit".text = cfge.loginShellInit;