diff --git a/home/tmux/default.nix b/home/tmux/default.nix
index e554fd0..08aeb55 100644
--- a/home/tmux/default.nix
+++ b/home/tmux/default.nix
@@ -11,6 +11,19 @@ in
     enable = my.mkDisableOption "tmux terminal multiplexer";
 
     enablePassthrough = mkEnableOption "tmux DCS passthrough sequence";
+
+    trueColorTerminals = mkOption {
+      type = with types; listOf str;
+      default = lib.my.nullableToList config.my.home.terminal.program;
+      defaultText = ''
+        `[ config.my.home.terminal.program ]` if it is non-null, otherwise an
+        empty list.
+      '';
+      example = [ "xterm-256color" ];
+      description = ''
+        $TERM values which should be considered to always support 24-bit color.
+      '';
+    };
   };
 
   config.programs.tmux = lib.mkIf cfg.enable {
@@ -75,6 +88,14 @@ in
           set -g allow-passthrough on
         ''
       }
+
+      # Force 24-bit color for each relevant $TERM
+      ${
+        let
+          mkTcFlag = term: ''set -as terminal-features ",${term}:RGB"'';
+        in
+        lib.concatMapStringsSep "\n" mkTcFlag cfg.trueColorTerminals
+      }
     '';
   };
 }
diff --git a/hosts/homes/ambroisie@mousqueton/default.nix b/hosts/homes/ambroisie@mousqueton/default.nix
index ac73da6..7f9d659 100644
--- a/hosts/homes/ambroisie@mousqueton/default.nix
+++ b/hosts/homes/ambroisie@mousqueton/default.nix
@@ -20,8 +20,6 @@
   # I use scripts that use the passthrough sequence often on this host
   my.home.tmux.enablePassthrough = true;
 
-  programs.tmux.extraConfig = ''
-    # Setup 24-bit color explicitly, as the default terminfo entry does not
-    set-option -sa terminal-overrides ",xterm-256color:Tc"
-  '';
+  # HTerm uses `xterm-256color` as its `$TERM`, so use that here
+  my.home.tmux.trueColorTerminals = [ "xterm-256color" ];
 }
diff --git a/lib/lists.nix b/lib/lists.nix
index 190198e..6c2fadd 100644
--- a/lib/lists.nix
+++ b/lib/lists.nix
@@ -24,4 +24,10 @@ in
   #   (any -> value)
   #   [ any ]
   mapFilter = pred: f: attrs: filter pred (map f attrs);
+
+  # Transform a nullable value into a list of zero/one element.
+  #
+  # nullableToList ::
+  #   (nullable a) -> [ a ]
+  nullableToList = x: if x != null then [ x ] else [ ];
 }