diff --git a/piet-gpu/shader/coarse.comp b/piet-gpu/shader/coarse.comp
index 12ec348..e540614 100644
--- a/piet-gpu/shader/coarse.comp
+++ b/piet-gpu/shader/coarse.comp
@@ -169,6 +169,8 @@ void main() {
         uint tile_count;
         switch (tag) {
         case Annotated_Fill:
+        case Annotated_FillMask:
+        case Annotated_FillMaskInv:
         case Annotated_Stroke:
         case Annotated_BeginClip:
         case Annotated_EndClip:
@@ -308,6 +310,27 @@ void main() {
                 Cmd_EndClip_write(cmd_ref, CmdEndClip(1.0));
                 cmd_ref.offset += Cmd_size;
                 break;
+            case Annotated_FillMask:
+            case Annotated_FillMaskInv:
+                tile = Tile_read(TileRef(sh_tile_base[element_ref_ix]
+                    + (sh_tile_stride[element_ref_ix] * tile_y + tile_x) * Tile_size));
+                AnnoFillMask fill_mask = Annotated_FillMask_read(ref);
+                alloc_cmd(cmd_ref, cmd_limit);
+                if (tile.tile.offset != 0) {
+                    CmdFillMask cmd_fill;
+                    cmd_fill.tile_ref = tile.tile.offset;
+                    cmd_fill.backdrop = tile.backdrop;
+                    cmd_fill.mask = fill_mask.mask;
+                    if (tag == Annotated_FillMask) {
+                        Cmd_FillMask_write(cmd_ref, cmd_fill);
+                    } else {
+                        Cmd_FillMaskInv_write(cmd_ref, cmd_fill);
+                    }
+                } else {
+                    Cmd_SolidMask_write(cmd_ref, CmdSolidMask(fill_mask.mask));
+                }
+                cmd_ref.offset += Cmd_size;
+                break;
             case Annotated_Stroke:
                 tile = Tile_read(TileRef(sh_tile_base[element_ref_ix]
                     + (sh_tile_stride[element_ref_ix] * tile_y + tile_x) * Tile_size));