diff --git a/d2m/event-dispatcher.js b/d2m/event-dispatcher.js
index 6c872fb..3544064 100644
--- a/d2m/event-dispatcher.js
+++ b/d2m/event-dispatcher.js
@@ -26,9 +26,11 @@ const updatePins = sync.require("./actions/update-pins")
 /** @type {import("../matrix/api")}) */
 const api = sync.require("../matrix/api")
 /** @type {import("../discord/utils")} */
-const utils = sync.require("../discord/utils")
+const dUtils = sync.require("../discord/utils")
 /** @type {import("../discord/discord-command-handler")}) */
 const discordCommandHandler = sync.require("../discord/discord-command-handler")
+/** @type {import("../m2d/converters/utils")} */
+const mxUtils = require("../m2d/converters/utils")
 
 /** @type {any} */ // @ts-ignore bad types from semaphore
 const Semaphore = require("@chriscdn/promise-semaphore")
@@ -68,20 +70,17 @@ module.exports = {
 				stackLines = stackLines.slice(0, cloudstormLine - 2)
 			}
 		}
-		let formattedBody = "\u26a0 <strong>Bridged event from Discord not delivered</strong>"
-			+ `<br>Gateway event: ${gatewayMessage.t}`
-			+ `<br>${e.toString()}`
+
+		const builder = new mxUtils.MatrixStringBuilder()
+		builder.addLine("\u26a0 Bridged event from Discord not delivered", "\u26a0 <strong>Bridged event from Discord not delivered</strong>")
+		builder.addLine(`Gateway event: ${gatewayMessage.t}`)
+		builder.addLine(e.toString())
 		if (stackLines) {
-			formattedBody += `<br><details><summary>Error trace</summary>`
-				+ `<pre>${stackLines.join("\n")}</pre></details>`
+			builder.addLine(`Error trace:\n${stackLines.join("\n")}`, `<details><summary>Error trace</summary><pre>${stackLines.join("\n")}</pre></details>`)
 		}
-		formattedBody += `<details><summary>Original payload</summary>`
-			+ `<pre>${util.inspect(gatewayMessage.d, false, 4, false)}</pre></details>`,
+		builder.addLine("", `<details><summary>Original payload</summary><pre>${util.inspect(gatewayMessage.d, false, 4, false)}</pre></details>`)
 		api.sendEvent(roomID, "m.room.message", {
-			msgtype: "m.text",
-			body: "\u26a0 Bridged event from Discord not delivered. See formatted content for full details.",
-			format: "org.matrix.custom.html",
-			formatted_body: formattedBody,
+			...builder.get(),
 			"moe.cadence.ooye.error": {
 				source: "discord",
 				payload: gatewayMessage
@@ -113,7 +112,7 @@ module.exports = {
 			const member = guild.members.find(m => m.user?.id === client.user.id)
 			if (!member) return
 			if (!("permission_overwrites" in channel)) continue
-			const permissions = utils.getPermissions(member.roles, guild.roles, client.user.id, channel.permission_overwrites)
+			const permissions = dUtils.getPermissions(member.roles, guild.roles, client.user.id, channel.permission_overwrites)
 			const wants = BigInt(1 << 10) | BigInt(1 << 16) // VIEW_CHANNEL + READ_MESSAGE_HISTORY
 			if ((permissions & wants) !== wants) continue // We don't have permission to look back in this channel
 
@@ -162,7 +161,7 @@ module.exports = {
 			const lastPin = updatePins.convertTimestamp(channel.last_pin_timestamp)
 
 			// Permissions check
-			const permissions = utils.getPermissions(member.roles, guild.roles, client.user.id, channel.permission_overwrites)
+			const permissions = dUtils.getPermissions(member.roles, guild.roles, client.user.id, channel.permission_overwrites)
 			const wants = BigInt(1 << 10) | BigInt(1 << 16) // VIEW_CHANNEL + READ_MESSAGE_HISTORY
 			if ((permissions & wants) !== wants) continue // We don't have permission to look up the pins in this channel
 
diff --git a/m2d/converters/utils.js b/m2d/converters/utils.js
index b820864..8a83a07 100644
--- a/m2d/converters/utils.js
+++ b/m2d/converters/utils.js
@@ -72,7 +72,7 @@ class MatrixStringBuilder {
 
 	/**
 	 * @param {string} body
-	 * @param {string} formattedBody
+	 * @param {string} [formattedBody]
 	 * @param {any} [condition]
 	 */
 	add(body, formattedBody, condition = true) {
diff --git a/m2d/converters/utils.test.js b/m2d/converters/utils.test.js
index 9d039fe..76fd824 100644
--- a/m2d/converters/utils.test.js
+++ b/m2d/converters/utils.test.js
@@ -1,7 +1,10 @@
 // @ts-check
 
+const e = new Error("Custom error")
+
 const {test} = require("supertape")
-const {eventSenderIsFromDiscord, getEventIDHash} = require("./utils")
+const {eventSenderIsFromDiscord, getEventIDHash, MatrixStringBuilder} = require("./utils")
+const util = require("util")
 
 test("sender type: matrix user", t => {
 	t.notOk(eventSenderIsFromDiscord("@cadence:cadence.moe"))
@@ -23,3 +26,51 @@ test("event hash: hash is the same each time", t => {
 test("event hash: hash is different for different inputs", t => {
 	t.notEqual(getEventIDHash("$Ij3qo7NxMA4VPexlAiIx2CB9JbsiGhJeyt-2OvkAUe1"), getEventIDHash("$Ij3qo7NxMA4VPexlAiIx2CB9JbsiGhJeyt-2OvkAUe2"))
 })
+
+test("MatrixStringBuilder: add, addLine, add same text", t => {
+	const gatewayMessage = {t: "MY_MESSAGE", d: {display: "Custom message data"}}
+	let stackLines = e.stack?.split("\n")
+
+	const builder = new MatrixStringBuilder()
+	builder.addLine("\u26a0 Bridged event from Discord not delivered", "\u26a0 <strong>Bridged event from Discord not delivered</strong>")
+	builder.addLine(`Gateway event: ${gatewayMessage.t}`)
+	builder.addLine(e.toString())
+	if (stackLines) {
+		stackLines = stackLines.slice(0, 2)
+		stackLines[1] = stackLines[1].replace(/\\/g, "/").replace(/(\s*at ).*(\/m2d\/)/, "$1.$2")
+		builder.addLine(`Error trace:`, `<details><summary>Error trace</summary>`)
+		builder.add(`\n${stackLines.join("\n")}`, `<pre>${stackLines.join("\n")}</pre></details>`)
+	}
+	builder.addLine("", `<details><summary>Original payload</summary><pre>${util.inspect(gatewayMessage.d, false, 4, false)}</pre></details>`)
+
+	t.deepEqual(builder.get(), {
+		msgtype: "m.text",
+		body: "\u26a0 Bridged event from Discord not delivered"
+			+ "\nGateway event: MY_MESSAGE"
+			+ "\nError: Custom error"
+			+ "\nError trace:"
+			+ "\nError: Custom error"
+			+ "\n    at ./m2d/converters/utils.test.js:3:11)\n",
+		format: "org.matrix.custom.html",
+		formatted_body: "\u26a0 <strong>Bridged event from Discord not delivered</strong>"
+			+ "<br>Gateway event: MY_MESSAGE"
+			+ "<br>Error: Custom error"
+			+ "<br><details><summary>Error trace</summary><pre>Error: Custom error\n    at ./m2d/converters/utils.test.js:3:11)</pre></details>"
+			+ `<details><summary>Original payload</summary><pre>{ display: 'Custom message data' }</pre></details>`
+	})
+})
+
+test("MatrixStringBuilder: complete code coverage", t => {
+	const builder = new MatrixStringBuilder()
+	builder.add("Line 1")
+	builder.addParagraph("Line 2")
+	builder.add("Line 3")
+	builder.addParagraph("Line 4")
+
+	t.deepEqual(builder.get(), {
+		msgtype: "m.text",
+		body: "Line 1\n\nLine 2Line 3\n\nLine 4",
+		format: "org.matrix.custom.html",
+		formatted_body: "Line 1<p>Line 2</p>Line 3<p>Line 4</p>"
+	})
+})