diff --git a/src/transforms/group.js b/src/transforms/group.js
index db419d32d0..a6f678e3f2 100644
--- a/src/transforms/group.js
+++ b/src/transforms/group.js
@@ -87,8 +87,8 @@ function group2(xv, yv, {z, fill, stroke, weight, domain, normalize, ...options}
           if (normalize === "facet") n = W ? sum(facet, i => W[i]) : facet.length;
           for (const [, I] of groups(facet, G)) {
             if (normalize === "z") n = W ? sum(I, i => W[i]) : I.length;
-            for (const [y, fy] of groups(I, Y, ydefined)) {
-              for (const [x, f] of groups(fy, X, xdefined)) {
+            for (const [y, fy] of groups(I, Y, ydefined, ydomain)) {
+              for (const [x, f] of groups(fy, X, xdefined, xdomain)) {
                 const l = W ? sum(f, i => W[i]) : f.length;
                 groupFacet.push(i++);
                 groupData.push(take(data, f));
@@ -129,8 +129,10 @@ function maybeNormalize(normalize) {
   throw new Error("invalid normalize");
 }
 
-export function groups(I, X, defined) {
+export function groups(I, X, defined, domain) {
   if (!X) return [[, I]];
   const G = grouper(I, i => X[i]);
-  return sort(defined ? Array.from(G).filter(defined) : G, first);
+  return domain
+    ? domain.map(x => [x, G.has(x) ? G.get(x) : []])
+    : sort(defined ? Array.from(G).filter(defined) : G, first);
 }
diff --git a/test/transforms/group-test.js b/test/transforms/group-test.js
new file mode 100644
index 0000000000..e06397533f
--- /dev/null
+++ b/test/transforms/group-test.js
@@ -0,0 +1,36 @@
+import * as Plot from "@observablehq/plot";
+import tape from "tape-await";
+
+tape("groupX respects the domain option (#255)", test => {
+  const data = ["A", "A", "C"];
+  const options = {x: d => d, domain: ["C", "B", "A"]};
+  const mark = Plot.dot(data, Plot.groupX(options));
+  const A = mark.initialize();
+  test.deepEqual(A.index, [0, 1, 2]);
+  test.deepEqual(A.channels.find(d => d[0] === "x")[1].value, ["C", "B", "A"]);
+  test.deepEqual(A.channels.find(d => d[0] === "y")[1].value, [1, 0, 2]);
+});
+
+tape("groupY respects the domain option (#255)", test => {
+  const data = ["A", "A", "C"];
+  const options = {x: d => d, domain: ["C", "B", "A"]};
+  const mark = Plot.dot(data, Plot.groupY(options));
+  const A = mark.initialize();
+  test.deepEqual(A.index, [0, 1, 2]);
+  test.deepEqual(A.channels.find(d => d[0] === "y")[1].value, ["C", "B", "A"]);
+  test.deepEqual(A.channels.find(d => d[0] === "x")[1].value, [1, 0, 2]);
+});
+
+tape("group respects the domain option (#255)", test => {
+  const data = ["A", "A", "C", "A", "C"];
+  const options = {x: d => d, y: d => d, domain: ["C", "B", "A"]};
+  const mark = Plot.dot(data, Plot.group(options));
+  const A = mark.initialize();
+  test.deepEqual(A.index, [0, 1, 2, 3, 4, 5, 6, 7, 8]);
+  test.deepEqual(A.channels.find(d => d[0] === "fill")[1].value, [
+  //C, B, A
+    2, 0, 0, // C
+    0, 0, 0, // B
+    0, 0, 3  // A
+  ]);
+});