diff --git a/nixos/modules/installer/cd-dvd/iso-image.nix b/nixos/modules/installer/cd-dvd/iso-image.nix
index 28c42d64f6f..6250fac0f0b 100644
--- a/nixos/modules/installer/cd-dvd/iso-image.nix
+++ b/nixos/modules/installer/cd-dvd/iso-image.nix
@@ -179,7 +179,6 @@ in
 
     fileSystems."/" =
       { fsType = "tmpfs";
-        device = "none";
         options = "mode=0755";
       };
 
@@ -201,7 +200,6 @@ in
 
     fileSystems."/nix/.rw-store" =
       { fsType = "tmpfs";
-        device = "none";
         options = "mode=0755";
         neededForBoot = true;
       };
diff --git a/nixos/modules/tasks/filesystems.nix b/nixos/modules/tasks/filesystems.nix
index d00f479754f..ccb6b616015 100644
--- a/nixos/modules/tasks/filesystems.nix
+++ b/nixos/modules/tasks/filesystems.nix
@@ -9,7 +9,7 @@ let
 
   prioOption = prio: optionalString (prio !=null) " pri=${toString prio}";
 
-  fileSystemOpts = { name, ... }: {
+  fileSystemOpts = { name, config, ... }: {
 
     options = {
 
@@ -68,6 +68,7 @@ let
 
     config = {
       mountPoint = mkDefault name;
+      device = mkIf (config.fsType == "tmpfs") config.fsType;
     };
 
   };
diff --git a/nixos/tests/misc.nix b/nixos/tests/misc.nix
index c03db6c4335..e1830d95b41 100644
--- a/nixos/tests/misc.nix
+++ b/nixos/tests/misc.nix
@@ -12,8 +12,7 @@ import ./make-test.nix {
       services.nixosManual.enable = mkOverride 0 true;
       systemd.tmpfiles.rules = [ "d /tmp 1777 root root 10d" ];
       fileSystems = mkVMOverride { "/tmp2" =
-        { device = "none";
-          fsType = "tmpfs";
+        { fsType = "tmpfs";
           options = "mode=1777,noauto";
         };
       };