diff --git a/hosts/by-name/moby/polyfill.nix b/hosts/by-name/moby/polyfill.nix
index c0512976..e2076793 100644
--- a/hosts/by-name/moby/polyfill.nix
+++ b/hosts/by-name/moby/polyfill.nix
@@ -30,6 +30,8 @@
     workspace_layout = "tabbed";
   };
 
+  sane.programs.waybar.fontSize = 14;
+
   sane.gui.sxmo = {
     nogesture = true;
     settings = {
diff --git a/hosts/common/programs/waybar/default.nix b/hosts/common/programs/waybar/default.nix
index 8002d4a8..45f0c4c2 100644
--- a/hosts/common/programs/waybar/default.nix
+++ b/hosts/common/programs/waybar/default.nix
@@ -7,18 +7,20 @@ in
     configOption = with lib; mkOption {
       type = types.submodule {
         options = {
-          extra_style = mkOption {
+          extraStyle = mkOption {
             type = types.lines;
-            default = ''
-              /* default font-size is about 14px, which is good for moby, but not quite for larger displays */
-              window#waybar {
-                font-size: 16px;
-              }
-            '';
+            default = "";
             description = ''
               extra CSS rules to append to ~/.config/waybar/style.css
             '';
           };
+          fontSize = mkOption {
+            type = types.int;
+            default = 16;
+            description = ''
+              default font-size is about 14px, which is good for moby, but not quite for larger displays
+            '';
+          };
           top = mkOption {
             type = types.submodule {
               # `attrsOf types.anything` (v.s. plain `attrs`) causes merging of the toplevel items.
@@ -80,8 +82,10 @@ in
       (pkgs.formats.json {}).generate "waybar-config.json" [
         ({ layer = "top"; } // cfg.config.top)
       ];
-    fs.".config/waybar/style.css".symlink.text =
-      (builtins.readFile ./waybar-style.css) + cfg.config.extra_style;
+    fs.".config/waybar/style.css".symlink.target = pkgs.substituteAll {
+      src = ./waybar-style.css;
+      inherit (cfg.config) extraStyle fontSize;
+    };
 
     services.waybar = {
       description = "swaybar graphical header bar/tray for sway";
diff --git a/hosts/common/programs/waybar/waybar-style.css b/hosts/common/programs/waybar/waybar-style.css
index fd65a752..556db352 100644
--- a/hosts/common/programs/waybar/waybar-style.css
+++ b/hosts/common/programs/waybar/waybar-style.css
@@ -14,6 +14,7 @@ window#waybar {
   color: #ffffff;
   transition-property: background-color;
   transition-duration: .2s;
+  font-size: @fontSize@px;
 }
 
 .modules-right {
@@ -99,3 +100,5 @@ window#waybar {
   -gtk-icon-effect: highlight;
   background-color: #e64291;
 }
+
+@extraStyle@
diff --git a/hosts/modules/gui/sxmo/default.nix b/hosts/modules/gui/sxmo/default.nix
index 0462ad00..aeed6a55 100644
--- a/hosts/modules/gui/sxmo/default.nix
+++ b/hosts/modules/gui/sxmo/default.nix
@@ -285,8 +285,7 @@ in
         sane.programs.sway.enableFor.user.colin = true;
         sane.programs.waybar.config = {
           top = import ./waybar-top.nix;
-          # reset extra waybar style
-          extra_style = "";
+          fontSize = 14;
         };
         sane.programs.sway.config = {
           # N.B. missing from upstream sxmo config here is: