diff --git a/src/portal.js b/src/portal.js
index 03516e3c..99cdfa76 100644
--- a/src/portal.js
+++ b/src/portal.js
@@ -13,9 +13,9 @@
 //
 // You should have received a copy of the GNU General Public License
 // along with this program.  If not, see <http://www.gnu.org/licenses/>.
+const md5 = require("md5")
 const TelegramPeer = require("./telegram-peer")
 const formatter = require("./formatter")
-const chalk = require("chalk")
 
 /**
  * Portal represents a portal from a Matrix room to a Telegram chat.
@@ -28,6 +28,10 @@ class Portal {
 		this.roomID = roomID
 		this.peer = peer
 		this.accessHashes = new Map()
+		// deduplicate duplication caused by telegram-mtproto bugs
+		this.lastMessageIDs = new Map()
+		// deduplicate duplication caused by multiple users
+		this.messageHashes = []
 	}
 
 	/**
@@ -230,6 +234,14 @@ class Portal {
 			await this.createMatrixRoom(evt.source, { invite: [evt.source.matrixUser.userID] })
 			return
 		}
+		if (evt.id) {
+			const last = this.lastMessageIDs.get(evt.source.userID)
+			if (last && evt.id <= last) {
+				this.app.debug(`Received old/duplicate message with ID ${evt.id} (latest ID: ${last})`)
+				return
+			}
+		}
+		this.lastMessageIDs.set(evt.source.userID, evt.id)
 		let matrixUser, telegramUser
 		switch (evt.action._) {
 		case "messageActionChatCreate":
@@ -330,6 +342,33 @@ class Portal {
 		return false
 	}
 
+	hash(evt) {
+		// Including the timestamp in the hash prevents reliably deduplicating multiuser-caused duplicates of
+		// Matrix-sent messages.
+		let base = (evt.text || evt.caption) + /*evt.date +*/ evt.from + evt.fwdFrom + evt.to.id
+		if (evt.geo) {
+			base += evt.geo.lat
+			base += evt.geo.long
+		} else if (evt.document) {
+			base += evt.document.id
+		} else if (evt.photo) {
+			base += evt.photo.id
+		}
+		return md5(base)
+	}
+
+	deduplicate(evt) {
+		const hashed = this.hash(evt)
+		if (this.messageHashes.includes(hashed)) {
+			return true
+		}
+		this.messageHashes.unshift(hashed)
+		if (this.messageHashes.length > 20) {
+			this.messageHashes.length = 20
+		}
+		return false
+	}
+
 	/**
 	 * Handle a Telegram service message event.
 	 *
@@ -347,8 +386,6 @@ class Portal {
 	 * @param {messageMediaGeo}      [evt.geo]      The Telegram {@link https://tjhorner.com/tl-schema/constructor/messageMediaGeo Location} attached to the message.
 	 */
 	async handleTelegramMessage(evt) {
-		const a = Object.assign({}, evt)
-		delete a.source
 		if (!this.isMatrixRoomCreated()) {
 			try {
 				const result = await this.createMatrixRoom(evt.source, { invite: [evt.source.matrixUser.userID] })
@@ -362,6 +399,10 @@ class Portal {
 			}
 		}
 
+		if (this.deduplicate(evt)) {
+			return
+		}
+
 		const sender = await this.app.getTelegramUser(evt.from)
 		try {
 			await sender.intent.sendTyping(this.roomID, false)
@@ -424,6 +465,16 @@ class Portal {
 					evt.content.formatted_body || evt.content.body,
 					evt.content.format === "org.matrix.custom.html",
 					this.app)
+			// evt.text || evt.caption) + evt.date + evt.from + evt.fwdFrom + evt.to.id)
+			this.deduplicate({
+				text: message,
+				date: Math.round(Date.now() / 1000),
+				from: sender.telegramPuppet.userID,
+				fwdFrom: 0,
+				to: {
+					id: this.peer.id,
+				},
+			})
 			await sender.telegramPuppet.sendMessage(this.peer, message, entities)
 			break
 		case "m.video":
@@ -440,6 +491,16 @@ class Portal {
 			break
 		case "m.location":
 			const [, lat, long] = /geo:([-]?[0-9]+\.[0-9]+)+,([-]?[0-9]+\.[0-9]+)/.exec()
+			this.deduplicate({
+				text: message,
+				date: Math.round(Date.now() / 1000),
+				from: sender.telegramPuppet.userID,
+				fwdFrom: 0,
+				to: {
+					id: this.peer.id,
+				},
+				geo: {lat, long },
+			})
 			await sender.telegramPuppet.sendMedia(this.peer, {
 				_: "inputMediaGeoPoint",
 				geo_point: {
diff --git a/src/telegram-puppet.js b/src/telegram-puppet.js
index 96233308..c6b96207 100644
--- a/src/telegram-puppet.js
+++ b/src/telegram-puppet.js
@@ -351,13 +351,6 @@ class TelegramPuppet {
 		if (update._ === "messageService" && update.action._ === "messageActionChannelMigrateFrom") {
 			return
 		}
-		if (update.id) {
-			if (update.id <= this.lastID) {
-				this.app.debug(`Received old/duplicate message with ID ${update.id} (latest ID: ${this.lastID})`)
-				return
-			}
-			this.lastID = update.id
-		}
 
 		portal = await this.app.getPortalByPeer(to)
 		if (update._ === "messageService") {
@@ -372,6 +365,8 @@ class TelegramPuppet {
 		await portal.handleTelegramMessage({
 			from,
 			to,
+			id: update.id,
+			date: update.date,
 			fwdFrom: update.fwd_from ? update.fwd_from.from_id : 0,
 			source: this,
 			text: update.message,
@@ -391,6 +386,8 @@ class TelegramPuppet {
 		})
 	}
 
+
+
 	async handleUpdate(data) {
 		if (!data.update || data.update._ !== "updateUserStatus") {
 			this.app.debug("green", "Raw event for", this.userID, JSON.stringify(data, "", "  "))
@@ -427,6 +424,10 @@ class TelegramPuppet {
 					date: this.date,
 					qts: -1,
 				})
+				if (dat._ === "updates.differenceEmpty") {
+					this.date = dat.date
+					break
+				}
 				this.app.debug("magenta", `updates.getDifference: ${JSON.stringify(dat, "", "  ")}`)
 				// TODO use dat.users and dat.chats
 				this.pts = dat.state.pts