diff --git a/nixos/modules/services/x11/xserver.nix b/nixos/modules/services/x11/xserver.nix
index b5fece488205..9ac69195a679 100644
--- a/nixos/modules/services/x11/xserver.nix
+++ b/nixos/modules/services/x11/xserver.nix
@@ -31,36 +31,51 @@ let
       pkgs.xorg.fontadobe75dpi
     ];
 
+  xrandrOptions = {
+    output = mkOption {
+      type = types.str;
+      example = "DVI-0";
+      description = ''
+        The output name of the monitor, as shown by <citerefentry>
+          <refentrytitle>xrandr</refentrytitle>
+          <manvolnum>1</manvolnum>
+        </citerefentry> invoked without arguments.
+      '';
+    };
+
+    primary = mkOption {
+      type = types.bool;
+      default = false;
+      description = ''
+        Whether this head is treated as the primary monitor,
+      '';
+    };
+
+    monitorConfig = mkOption {
+      type = types.lines;
+      default = "";
+      example = ''
+        DisplaySize 408 306
+        Option "DPMS" "false"
+      '';
+      description = ''
+        Extra lines to append to the <literal>Monitor</literal> section
+        verbatim.
+      '';
+    };
+  };
 
   # Just enumerate all heads without discarding XRandR output information.
-  xrandrHeads = (
-    fold
-      (nextHead: { index, alreadyPrimary, processedHeads }:
-        let
-          processedHead = { name = "multihead${toString index}"; } // 
-            (if isAttrs nextHead then
-              {
-                output = nextHead.output;
-                primary = if alreadyPrimary then false else nextHead.primary || index == 0;
-                monitorConfig = nextHead.monitorConfig;
-              }
-            else
-              {
-                output = nextHead;
-                primary = if alreadyPrimary then false else index == 0;
-                monitorConfig = "";
-              }
-            );
-          primariness = if alreadyPrimary then true else processedHead.primary;
-        in
-          { index = index - 1; alreadyPrimary = primariness; processedHeads = ([ processedHead ] ++ processedHeads); })
-      { index = (length cfg.xrandrHeads) - 1; alreadyPrimary = false; processedHeads = []; }
-      cfg.xrandrHeads
-  ).processedHeads;
+  xrandrHeads = let
+    mkHead = num: config: {
+      name = "multihead${toString num}";
+      inherit config;
+    };
+  in imap mkHead cfg.xrandrHeads;
 
   xrandrDeviceSection = let
     monitors = flip map xrandrHeads (h: ''
-      Option "monitor-${h.output}" "${h.name}"
+      Option "monitor-${h.config.output}" "${h.name}"
     '');
     # First option is indented through the space in the config but any
     # subsequent options aren't so we need to apply indentation to
@@ -80,13 +95,13 @@ let
       value = ''
         Section "Monitor"
           Identifier "${current.name}"
-          ${optionalString (current.primary) ''
+          ${optionalString (current.config.primary) ''
           Option "Primary" "true"
           ''}
           ${optionalString (previous != []) ''
           Option "RightOf" "${(head previous).name}"
           ''}
-          ${current.monitorConfig}
+          ${current.config.monitorConfig}
         EndSection
       '';
     } ++ previous;
@@ -351,27 +366,36 @@ in
 
       xrandrHeads = mkOption {
         default = [];
-        example = [ "HDMI-0" { output = "DVI-0"; primary = true; monitorConfig = ""; } ];
-        type = with types; listOf (either
-          str
-          (submodule {
-            options.output = str;
-            options.primary = bool;
-            options.monitorConfig = lines;
-          })
-        );
+        example = [
+          "HDMI-0"
+          { output = "DVI-0"; primary = true; }
+          { output = "DVI-1"; monitorConfig = "Option \"Rotate\" \"left\""; }
+        ];
+        type = with types; listOf (coercedTo str (output: {
+          inherit output;
+        }) (submodule { options = xrandrOptions; }));
+        apply = heads: let
+          hasPrimary = any (x: x.primary) heads;
+          firstPrimary = head heads // { primary = true; };
+          newHeads = singleton firstPrimary ++ tail heads;
+        in if heads != [] && !hasPrimary then newHeads else heads;
         description = ''
-          Simple multiple monitor configuration, just specify a list of XRandR
-          outputs as the values of the list. The monitors will be mapped from
-          left to right in the order of the list.
+          Multiple monitor configuration, just specify a list of XRandR
+          outputs. The individual elements should be either simple strings or
+          an attribute set of output options.
 
-          By default, the first monitor will be set as the primary monitor.
-          However instead of a list, you can give an attribute set. That set
-          can contain a primary monitor specification and a custom monitor
-          configuration section.
+          If the element is a string, it is denoting the physical output for a
+          monitor, if it's an attribute set, you must at least provide the
+          <option>output</option> option.
 
-          Only one monitor is allowed to be primary. If multiple monitors are
-          specified as primary, only the last monitor will be primary.
+          The monitors will be mapped from left to right in the order of the
+          list.
+
+          By default, the first monitor will be set as the primary monitor if
+          none of the elements contain an option that has set
+          <option>primary</option> to <literal>true</literal>.
+
+          <note><para>Only one monitor is allowed to be primary.</para></note>
 
           Be careful using this option with multiple graphic adapters or with
           drivers that have poor support for XRandR, unexpected things might
@@ -506,11 +530,18 @@ in
 
     nixpkgs.config.xorg = optionalAttrs (elem "vboxvideo" cfg.videoDrivers) { abiCompat = "1.18"; };
 
-    assertions =
-      [ { assertion = config.security.polkit.enable;
-          message = "X11 requires Polkit to be enabled (‘security.polkit.enable = true’).";
-        }
-      ];
+    assertions = [
+      { assertion = config.security.polkit.enable;
+        message = "X11 requires Polkit to be enabled (‘security.polkit.enable = true’).";
+      }
+      (let primaryHeads = filter (x: x.primary) cfg.xrandrHeads; in {
+        assertion = length primaryHeads < 2;
+        message = "Only one head is allowed to be primary in "
+                + "‘services.xserver.xrandrHeads’, but there are "
+                + "${toString (length primaryHeads)} heads set to primary: "
+                + concatMapStringsSep ", " (x: x.output) primaryHeads;
+      })
+    ];
 
     environment.etc =
       (optionals cfg.exportConfiguration