diff --git a/src/matrix/api.js b/src/matrix/api.js
index edffc45..6d135bd 100644
--- a/src/matrix/api.js
+++ b/src/matrix/api.js
@@ -378,19 +378,26 @@ async function ping() {
 }
 
 /**
+ * Given an mxc:// URL, and an optional height for thumbnailing, get the file from the content repository. Returns res.
  * @param {string} mxc
- * @param {RequestInit} [init]
+ * @param {RequestInit & {height?: number | string}} [init]
  * @return {Promise<Response & {body: streamWeb.ReadableStream<Uint8Array>}>}
  */
 async function getMedia(mxc, init = {}) {
 	const mediaParts = mxc?.match(/^mxc:\/\/([^/]+)\/(\w+)$/)
 	assert(mediaParts)
-	const res = await fetch(`${mreq.baseUrl}/client/v1/media/download/${mediaParts[1]}/${mediaParts[2]}`, {
+	const downloadOrThumbnail = init.height ? "thumbnail" : "download"
+	let url = `${mreq.baseUrl}/client/v1/media/${downloadOrThumbnail}/${mediaParts[1]}/${mediaParts[2]}`
+	if (init.height) url += "?" + new URLSearchParams({height: String(init.height), width: String(init.height)})
+	const res = await fetch(url, {
 		headers: {
 			Authorization: `Bearer ${reg.as_token}`
 		},
 		...init
 	})
+	if (res.status !== 200) {
+		throw mreq.makeMatrixServerError(res, init)
+	}
 	if (init.method !== "HEAD") {
 		assert(res.body)
 	}
diff --git a/src/matrix/mreq.js b/src/matrix/mreq.js
index 9179825..bed7951 100644
--- a/src/matrix/mreq.js
+++ b/src/matrix/mreq.js
@@ -18,6 +18,21 @@ class MatrixServerError extends Error {
 	}
 }
 
+/**
+ * @param {Response} res
+ * @param {object} opts
+ */
+async function makeMatrixServerError(res, opts = {}) {
+	delete opts.headers?.["Authorization"]
+	if (res.headers.get("content-type") === "application/json") {
+		return new MatrixServerError(await res.json(), opts)
+	} else if (res.headers.get("content-type")?.startsWith("text/")) {
+		return new MatrixServerError({errcode: "CX_SERVER_ERROR", error: `Server returned HTTP status ${res.status}`, message: await res.text()})
+	} else {
+		return new MatrixServerError({errcode: "CX_SERVER_ERROR", error: `Server returned HTTP status ${res.status}`, content_type: res.headers.get("content-type")})
+	}
+}
+
 /**
  * @param {undefined | string | object | streamWeb.ReadableStream | stream.Readable} body
  * @returns {Promise<string | streamWeb.ReadableStream | stream.Readable | Buffer>}
@@ -85,6 +100,7 @@ async function withAccessToken(token, callback) {
 }
 
 module.exports.MatrixServerError = MatrixServerError
+module.exports.makeMatrixServerError = makeMatrixServerError
 module.exports.baseUrl = baseUrl
 module.exports.mreq = mreq
 module.exports.withAccessToken = withAccessToken