diff --git a/src/ui/app.css b/src/ui/app.css
index 7b5bc08..12144ce 100644
--- a/src/ui/app.css
+++ b/src/ui/app.css
@@ -21,6 +21,7 @@
   --border: #e4e4e0;
   --sel: #cfe3f7;
   --caret: #d57d2c;
+  --error: #c1443a;
   --toolbar-bg: #fafaf8;
   --hover: #ececea;
 }
@@ -41,6 +42,7 @@
   --border: #333438;
   --sel: #2d4a68;
   --caret: #e8923c;
+  --error: #e2685c;
   --toolbar-bg: #232428;
   --hover: #2f3035;
 }
@@ -332,6 +334,10 @@ body {
   text-overflow: ellipsis;
 }
 .result-line:hover { text-decoration: underline; }
+.result-line.result-error {
+  color: var(--error);
+  font-style: italic;
+}
 .result-sparkline {
   position: absolute;
   right: 14px;
diff --git a/src/ui/editor.ts b/src/ui/editor.ts
index 0699eed..247a544 100644
--- a/src/ui/editor.ts
+++ b/src/ui/editor.ts
@@ -324,7 +324,8 @@ export class SumEditor {
     for (let i = 0; i < Math.min(this.results.length, doc.lines); i++) {
       const r = this.results[i];
       const isChart = r.value?.kind === "chart";
-      if (!r.text && !isChart) continue;
+      const isError = !!r.error;
+      if (!r.text && !isChart && !isError) continue;
       const line = doc.line(i + 1);
       const block = this.view.lineBlockAt(line.from);
       const top = docTop + block.top - overlayTop;
@@ -333,9 +334,10 @@ export class SumEditor {
         frag.appendChild(buildSparkline(r.value.points.map((p) => p.toNumber()), top));
       } else {
         const el = document.createElement("div");
-        el.className = "result-line";
-        el.textContent = r.text;
-        el.dataset.value = r.text!;
+        el.className = "result-line" + (isError ? " result-error" : "");
+        el.textContent = isError ? "#ref?" : r.text;
+        if (!isError) el.dataset.value = r.text!;
+        if (isError) el.title = r.error!;
         el.style.top = `${top}px`;
         frag.appendChild(el);
       }