diff --git a/web/src/api/types/preferences/localstorage.ts b/web/src/api/types/preferences/localstorage.ts
index c74c984..c4992a0 100644
--- a/web/src/api/types/preferences/localstorage.ts
+++ b/web/src/api/types/preferences/localstorage.ts
@@ -13,7 +13,7 @@
 //
 // You should have received a copy of the GNU Affero General Public License
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
-import { Preferences, existingPreferenceKeys, preferences } from "./preferences.ts"
+import { Preferences, isValidPreferenceKey, preferences } from "./preferences.ts"
 import { PreferenceContext } from "./types.ts"
 
 function getObjectFromLocalStorage(key: string): Preferences {
@@ -28,11 +28,18 @@ function getObjectFromLocalStorage(key: string): Preferences {
 	return {}
 }
 
+const globalPrefKeys = Object.entries(preferences)
+	.filter(([,pref]) => pref.allowedContexts.includes(PreferenceContext.Device))
+	.map(([key]) => key)
+const roomPrefKeys = Object.entries(preferences)
+	.filter(([,pref]) => pref.allowedContexts.includes(PreferenceContext.RoomDevice))
+	.map(([key]) => key)
+
 export function getLocalStoragePreferences(localStorageKey: string, onChange: () => void): Preferences {
 	return new Proxy(getObjectFromLocalStorage(localStorageKey), {
 		// eslint-disable-next-line @typescript-eslint/no-explicit-any
-		set(target: Preferences, key: keyof Preferences, newValue: any): boolean {
-			if (!existingPreferenceKeys.has(key)) {
+		set(target: Preferences, key: string | symbol, newValue: any): boolean {
+			if (!isValidPreferenceKey(key)) {
 				return false
 			}
 			target[key] = newValue
@@ -40,8 +47,8 @@ export function getLocalStoragePreferences(localStorageKey: string, onChange: ()
 			onChange()
 			return true
 		},
-		deleteProperty(target: Preferences, key: keyof Preferences): boolean {
-			if (!existingPreferenceKeys.has(key)) {
+		deleteProperty(target: Preferences, key: string | symbol): boolean {
+			if (!isValidPreferenceKey(key)) {
 				return false
 			}
 			delete target[key]
@@ -52,13 +59,15 @@ export function getLocalStoragePreferences(localStorageKey: string, onChange: ()
 			return true
 		},
 		ownKeys(): string[] {
-			console.warn("localStorage preference proxy ownKeys called")
-			// This is only for debugging, so the performance doesn't matter that much
-			return Object.entries(preferences)
-				.filter(([,pref]) =>
-					pref.allowedContexts.includes(localStorageKey === "global_prefs"
-						? PreferenceContext.Device : PreferenceContext.RoomDevice))
-				.map(([key]) => key)
+			return localStorageKey === "global_prefs" ? globalPrefKeys : roomPrefKeys
+		},
+		getOwnPropertyDescriptor(_target: never, key: string | symbol): PropertyDescriptor | undefined {
+			const keySet = localStorageKey === "global_prefs" ? globalPrefKeys : roomPrefKeys
+			return (typeof key === "string" && keySet.includes(key)) ? {
+				configurable: true,
+				enumerable: true,
+				writable: true,
+			} : undefined
 		},
 	})
 }
diff --git a/web/src/api/types/preferences/preferences.ts b/web/src/api/types/preferences/preferences.ts
index 6831a58..1404667 100644
--- a/web/src/api/types/preferences/preferences.ts
+++ b/web/src/api/types/preferences/preferences.ts
@@ -13,6 +13,7 @@
 //
 // You should have received a copy of the GNU Affero General Public License
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
+import type { ContentURI } from "../../types"
 import { Preference, anyContext } from "./types.ts"
 
 export const codeBlockStyles = [
@@ -56,7 +57,7 @@ export const preferences = {
 		allowedValues: codeBlockStyles,
 	}),
 	pointer_cursor: new Preference<boolean>({
-		displayName: "Pointer cursor",
+		displayName: "Use pointer cursor",
 		description: "Whether to use a pointer cursor for clickable elements.",
 		allowedContexts: anyContext,
 		defaultValue: false,
@@ -97,6 +98,12 @@ export const preferences = {
 		allowedContexts: anyContext,
 		defaultValue: true,
 	}),
+	custom_notification_sound: new Preference<ContentURI>({
+		displayName: "Custom notification sound",
+		description: "The mxc:// URI to a custom notification sound.",
+		allowedContexts: anyContext,
+		defaultValue: "",
+	}),
 } as const
 
 export const existingPreferenceKeys = new Set(Object.keys(preferences))
@@ -104,3 +111,7 @@ export const existingPreferenceKeys = new Set(Object.keys(preferences))
 export type Preferences = {
 	-readonly [name in keyof typeof preferences]?: typeof preferences[name]["defaultValue"]
 }
+
+export function isValidPreferenceKey(key: unknown): key is keyof Preferences {
+	return typeof key === "string" && existingPreferenceKeys.has(key)
+}
diff --git a/web/src/api/types/preferences/proxy.ts b/web/src/api/types/preferences/proxy.ts
index 97818bd..d9cd11a 100644
--- a/web/src/api/types/preferences/proxy.ts
+++ b/web/src/api/types/preferences/proxy.ts
@@ -14,18 +14,23 @@
 // You should have received a copy of the GNU Affero General Public License
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 import type { RoomStateStore, StateStore } from "@/api/statestore"
-import { Preferences, existingPreferenceKeys, preferences } from "./preferences.ts"
+import { Preferences, isValidPreferenceKey, preferences } from "./preferences.ts"
 import { PreferenceContext, PreferenceValueType } from "./types.ts"
 
+const prefKeys = Object.keys(preferences)
+
 export function getPreferenceProxy(store: StateStore, room?: RoomStateStore): Preferences {
 	return new Proxy({}, {
 		set(): boolean {
 			throw new Error("The preference proxy is read-only")
 		},
-		get(_target: never, key: keyof Preferences): PreferenceValueType | undefined {
+		get(_target: never, key: keyof Preferences | symbol): PreferenceValueType | undefined {
+			if (typeof key !== "string") {
+				return
+			}
 			const pref = preferences[key]
 			if (!pref) {
-				return undefined
+				return
 			}
 			let val: typeof pref.defaultValue | undefined
 			for (const ctx of pref.allowedContexts) {
@@ -47,7 +52,14 @@ export function getPreferenceProxy(store: StateStore, room?: RoomStateStore): Pr
 			return pref.defaultValue
 		},
 		ownKeys(): string[] {
-			return Array.from(existingPreferenceKeys)
+			return prefKeys
+		},
+		getOwnPropertyDescriptor(_target: never, key: string | symbol): PropertyDescriptor | undefined {
+			return isValidPreferenceKey(key) ? {
+				configurable: true,
+				enumerable: true,
+				writable: false,
+			} : undefined
 		},
 	})
 }