diff --git a/src/d2m/actions/update-pins.js b/src/d2m/actions/update-pins.js
index 6ef477f..15febaa 100644
--- a/src/d2m/actions/update-pins.js
+++ b/src/d2m/actions/update-pins.js
@@ -33,9 +33,10 @@ async function updatePins(channelID, roomID, convertedTimestamp) {
 		}
 		throw e
 	}
-	const pinned = pinsToList.pinsToList(discordPins)
 
 	const kstate = await ks.roomToKState(roomID)
+	const pinned = pinsToList.pinsToList(discordPins, kstate)
+
 	const diff = ks.diffKState(kstate, {"m.room.pinned_events/": {pinned}})
 	await ks.applyKStateDiffToRoom(roomID, diff)
 
diff --git a/src/d2m/converters/pins-to-list.js b/src/d2m/converters/pins-to-list.js
index 047bb9f..3e890ea 100644
--- a/src/d2m/converters/pins-to-list.js
+++ b/src/d2m/converters/pins-to-list.js
@@ -4,16 +4,28 @@ const {select} = require("../../passthrough")
 
 /**
  * @param {import("discord-api-types/v10").RESTGetAPIChannelPinsResult} pins
+ * @param {{"m.room.pinned_events/"?: {pinned?: string[]}}} kstate
  */
-function pinsToList(pins) {
+function pinsToList(pins, kstate) {
+	let alreadyPinned = kstate["m.room.pinned_events/"]?.pinned || []
+
+	// If any of the already pinned messages are bridged messages then remove them from the already pinned list.
+	//   * If a bridged message is still pinned then it'll be added back in the next step.
+	//   * If a bridged message was unpinned from Discord-side then it'll be unpinned from our side due to this step.
+	//   * Matrix-only unbridged messages that are pinned will remain pinned.
+	alreadyPinned = alreadyPinned.filter(event_id => {
+		const messageID = select("event_message", "message_id", {event_id}).pluck().get()
+		return !messageID || pins.find(m => m.id === messageID) // if it is bridged then remove it from the filter
+	})
+
 	/** @type {string[]} */
 	const result = []
 	for (const message of pins) {
 		const eventID = select("event_message", "event_id", {message_id: message.id, part: 0}).pluck().get()
-		if (eventID) result.push(eventID)
+		if (eventID && !alreadyPinned.includes(eventID)) result.push(eventID)
 	}
 	result.reverse()
-	return result
+	return alreadyPinned.concat(result)
 }
 
 module.exports.pinsToList = pinsToList
diff --git a/src/d2m/converters/pins-to-list.test.js b/src/d2m/converters/pins-to-list.test.js
index 7ee89b6..d0657cb 100644
--- a/src/d2m/converters/pins-to-list.test.js
+++ b/src/d2m/converters/pins-to-list.test.js
@@ -3,10 +3,59 @@ const data = require("../../../test/data")
 const {pinsToList} = require("./pins-to-list")
 
 test("pins2list: converts known IDs, ignores unknown IDs", t => {
-	const result = pinsToList(data.pins.faked)
+	const result = pinsToList(data.pins.faked, {})
 	t.deepEqual(result, [
 		"$lnAF9IosAECTnlv9p2e18FG8rHn-JgYKHEHIh5qdFv4",
 		"$mtR8cJqM4fKno1bVsm8F4wUVqSntt2sq6jav1lyavuA",
 		"$X16nfVks1wsrhq4E9SSLiqrf2N8KD0erD0scZG7U5xg"
 	])
 })
+
+test("pins2list: already pinned duplicate items are not moved", t => {
+	const result = pinsToList(data.pins.faked, {
+		"m.room.pinned_events/": {
+			pinned: [
+				"$mtR8cJqM4fKno1bVsm8F4wUVqSntt2sq6jav1lyavuA"
+			]
+		}
+	})
+	t.deepEqual(result, [
+		"$mtR8cJqM4fKno1bVsm8F4wUVqSntt2sq6jav1lyavuA",
+		"$lnAF9IosAECTnlv9p2e18FG8rHn-JgYKHEHIh5qdFv4",
+		"$X16nfVks1wsrhq4E9SSLiqrf2N8KD0erD0scZG7U5xg"
+	])
+})
+
+test("pins2list: already pinned unknown items are not moved", t => {
+	const result = pinsToList(data.pins.faked, {
+		"m.room.pinned_events/": {
+			pinned: [
+				"$unknown1",
+				"$mtR8cJqM4fKno1bVsm8F4wUVqSntt2sq6jav1lyavuA",
+				"$unknown2"
+			]
+		}
+	})
+	t.deepEqual(result, [
+		"$unknown1",
+		"$mtR8cJqM4fKno1bVsm8F4wUVqSntt2sq6jav1lyavuA",
+		"$unknown2",
+		"$lnAF9IosAECTnlv9p2e18FG8rHn-JgYKHEHIh5qdFv4",
+		"$X16nfVks1wsrhq4E9SSLiqrf2N8KD0erD0scZG7U5xg"
+	])
+})
+
+test("pins2list: bridged messages can be unpinned", t => {
+	const result = pinsToList(data.pins.faked.slice(0, -2), {
+		"m.room.pinned_events/": {
+			pinned: [
+				"$mtR8cJqM4fKno1bVsm8F4wUVqSntt2sq6jav1lyavuA",
+				"$lnAF9IosAECTnlv9p2e18FG8rHn-JgYKHEHIh5qdFv4"
+			]
+		}
+	})
+	t.deepEqual(result, [
+		"$mtR8cJqM4fKno1bVsm8F4wUVqSntt2sq6jav1lyavuA",
+		"$X16nfVks1wsrhq4E9SSLiqrf2N8KD0erD0scZG7U5xg",
+	])
+})