diff --git a/src/Avatar.test.tsx b/src/Avatar.test.tsx
index 9df6384c..0de68ce2 100644
--- a/src/Avatar.test.tsx
+++ b/src/Avatar.test.tsx
@@ -14,10 +14,9 @@ import { ClientContextProvider } from "./ClientContext";
 import { Avatar } from "./Avatar";
 import { mockMatrixRoomMember } from "./utils/test";
 
-const TestComponent: FC<PropsWithChildren<{ client: MatrixClient }>> = ({
-  client,
-  children,
-}) => {
+const TestComponent: FC<
+  PropsWithChildren<{ client: MatrixClient; supportsThumbnails?: boolean }>
+> = ({ client, children, supportsThumbnails }) => {
   return (
     <ClientContextProvider
       value={{
@@ -25,6 +24,7 @@ const TestComponent: FC<PropsWithChildren<{ client: MatrixClient }>> = ({
         disconnected: false,
         supportedFeatures: {
           reactions: true,
+          thumbnails: supportsThumbnails ?? true,
         },
         setClient: vi.fn(),
         authenticated: {
@@ -70,6 +70,34 @@ test("should just render a placeholder when the user has no avatar", () => {
   expect(element.tagName).toEqual("SPAN");
   expect(client.mxcUrlToHttp).toBeCalledTimes(0);
 });
+
+test("should just render a placeholder when thumbnaisl are not supported", () => {
+  const client = vi.mocked<MatrixClient>({
+    getAccessToken: () => "my-access-token",
+    mxcUrlToHttp: () => vi.fn(),
+  } as unknown as MatrixClient);
+
+  vi.spyOn(client, "mxcUrlToHttp");
+  const member = mockMatrixRoomMember({
+    userId: "@alice:example.org",
+    getMxcAvatarUrl: () => "mxc://example.org/alice-avatar",
+  });
+  const displayName = "Alice";
+  render(
+    <TestComponent client={client} supportsThumbnails={false}>
+      <Avatar
+        id={member.userId}
+        name={displayName}
+        size={96}
+        src={member?.getMxcAvatarUrl()}
+      />
+    </TestComponent>,
+  );
+  const element = screen.getByRole("img", { name: "@alice:example.org" });
+  expect(element.tagName).toEqual("SPAN");
+  expect(client.mxcUrlToHttp).toBeCalledTimes(0);
+});
+
 test("should attempt to fetch authenticated media", async () => {
   const expectedAuthUrl = "http://example.org/media/alice-avatar";
   const expectedObjectURL = "my-object-url";
diff --git a/src/Avatar.tsx b/src/Avatar.tsx
index a68c17f8..f3fe6cd8 100644
--- a/src/Avatar.tsx
+++ b/src/Avatar.tsx
@@ -9,7 +9,7 @@ import { useMemo, FC, CSSProperties, useState, useEffect } from "react";
 import { Avatar as CompoundAvatar } from "@vector-im/compound-web";
 import { MatrixClient } from "matrix-js-sdk/src/client";
 
-import { useClient } from "./ClientContext";
+import { useClientState } from "./ClientContext";
 
 export enum Size {
   XS = "xs",
@@ -67,7 +67,7 @@ export const Avatar: FC<Props> = ({
   style,
   ...props
 }) => {
-  const { client } = useClient();
+  const clientState = useClientState();
 
   const sizePx = useMemo(
     () =>
@@ -80,9 +80,16 @@ export const Avatar: FC<Props> = ({
   const [avatarUrl, setAvatarUrl] = useState<string | undefined>(undefined);
 
   useEffect(() => {
-    if (!client || !src || !sizePx) {
+    if (clientState?.state !== "valid") {
       return;
     }
+    const { authenticated, supportedFeatures } = clientState;
+    const client = authenticated?.client;
+
+    if (!client || !src || !sizePx || !supportedFeatures.thumbnails) {
+      return;
+    }
+
     const token = client.getAccessToken();
     if (!token) {
       return;
@@ -113,7 +120,7 @@ export const Avatar: FC<Props> = ({
         URL.revokeObjectURL(objectUrl);
       }
     };
-  }, [client, src, sizePx]);
+  }, [clientState, src, sizePx]);
 
   return (
     <CompoundAvatar
diff --git a/src/ClientContext.tsx b/src/ClientContext.tsx
index 07b78dad..7a37e750 100644
--- a/src/ClientContext.tsx
+++ b/src/ClientContext.tsx
@@ -48,6 +48,7 @@ export type ValidClientState = {
   disconnected: boolean;
   supportedFeatures: {
     reactions: boolean;
+    thumbnails: boolean;
   };
   setClient: (params?: SetClientParams) => void;
 };
@@ -255,6 +256,7 @@ export const ClientProvider: FC<Props> = ({ children }) => {
 
   const [isDisconnected, setIsDisconnected] = useState(false);
   const [supportsReactions, setSupportsReactions] = useState(false);
+  const [supportsThumbnails, setSupportsThumbnails] = useState(false);
 
   const state: ClientState | undefined = useMemo(() => {
     if (alreadyOpenedErr) {
@@ -280,6 +282,7 @@ export const ClientProvider: FC<Props> = ({ children }) => {
       disconnected: isDisconnected,
       supportedFeatures: {
         reactions: supportsReactions,
+        thumbnails: supportsThumbnails,
       },
     };
   }, [
@@ -290,6 +293,7 @@ export const ClientProvider: FC<Props> = ({ children }) => {
     setClient,
     isDisconnected,
     supportsReactions,
+    supportsThumbnails,
   ]);
 
   const onSync = useCallback(
@@ -315,6 +319,8 @@ export const ClientProvider: FC<Props> = ({ children }) => {
     }
 
     if (initClientState.widgetApi) {
+      // There is currently no widget API for authenticated media thumbnails.
+      setSupportsThumbnails(false);
       const reactSend = initClientState.widgetApi.hasCapability(
         "org.matrix.msc2762.send.event:m.reaction",
       );
@@ -336,6 +342,7 @@ export const ClientProvider: FC<Props> = ({ children }) => {
       }
     } else {
       setSupportsReactions(true);
+      setSupportsThumbnails(true);
     }
 
     return (): void => {