diff --git a/packages/carta-md/src/lib/internal/speculative.ts b/packages/carta-md/src/lib/internal/speculative.ts
index fd1f5a07..4e48b831 100644
--- a/packages/carta-md/src/lib/internal/speculative.ts
+++ b/packages/carta-md/src/lib/internal/speculative.ts
@@ -14,6 +14,10 @@ const clonePosition = (position: Position): Position => {
 	};
 };
 
+/** Escape text so it is parsed as text, and not as markup, by the overlay. */
+const escapeHtml = (text: string): string =>
+	text.replaceAll('&', '&amp;').replaceAll('<', '&lt;').replaceAll('>', '&gt;');
+
 /**
  * Temporary updates the highlight overlay to reflect the changes between two text strings,
  * waiting for the actual update to be applied. This way, the user can immediately see the changes,
@@ -32,7 +36,7 @@ export function speculativeHighlightUpdate(from: string, to: string, currentHTML
 	let writingPosition: Position = { line: 0, span: 0, char: 0 };
 	let readingPosition: Position = { line: 0, span: 0, char: 0 };
 
-	if (lines.length === 0) return to;
+	if (lines.length === 0) return escapeHtml(to);
 
 	const advance = () => {
 		writingPosition = clonePosition(readingPosition);