diff --git a/src/Roles.ts b/src/Roles.ts
index ae0d316d30..77c50fe64c 100644
--- a/src/Roles.ts
+++ b/src/Roles.ts
@@ -16,7 +16,7 @@ limitations under the License.
 
 import { _t } from './languageHandler';
 
-export function levelRoleMap(usersDefault: number) {
+export function levelRoleMap(usersDefault: number): Record<number | "undefined", string> {
     return {
         undefined: _t('Default'),
         0: _t('Restricted'),
diff --git a/src/components/views/elements/PowerSelector.tsx b/src/components/views/elements/PowerSelector.tsx
index 3a9e87d158..8b251b91a5 100644
--- a/src/components/views/elements/PowerSelector.tsx
+++ b/src/components/views/elements/PowerSelector.tsx
@@ -44,14 +44,13 @@ interface IProps {
 }
 
 interface IState {
-    levelRoleMap: {};
+    levelRoleMap: Partial<Record<number | "undefined", string>>;
     // List of power levels to show in the drop-down
     options: number[];
 
     customValue: number;
     selectValue: number | string;
     custom?: boolean;
-    customLevel?: number;
 }
 
 export default class PowerSelector extends React.Component<IProps, IState> {
@@ -101,7 +100,7 @@ export default class PowerSelector extends React.Component<IProps, IState> {
             levelRoleMap,
             options,
             custom: isCustom,
-            customLevel: newProps.value,
+            customValue: newProps.value,
             selectValue: isCustom ? CUSTOM_VALUE : newProps.value,
         });
     }
@@ -125,7 +124,11 @@ export default class PowerSelector extends React.Component<IProps, IState> {
         event.preventDefault();
         event.stopPropagation();
 
-        this.props.onChange(this.state.customValue, this.props.powerLevelKey);
+        if (Number.isFinite(this.state.customValue)) {
+            this.props.onChange(this.state.customValue, this.props.powerLevelKey);
+        } else {
+            this.initStateFromProps(this.props); // reset, invalid input
+        }
     };
 
     private onCustomKeyDown = (event: React.KeyboardEvent<HTMLInputElement>): void => {
diff --git a/test/components/views/elements/PowerSelector-test.tsx b/test/components/views/elements/PowerSelector-test.tsx
new file mode 100644
index 0000000000..9367d0b089
--- /dev/null
+++ b/test/components/views/elements/PowerSelector-test.tsx
@@ -0,0 +1,62 @@
+/*
+Copyright 2022 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import React from 'react';
+import { fireEvent, render, screen } from "@testing-library/react";
+
+import PowerSelector from "../../../../src/components/views/elements/PowerSelector";
+
+describe('<PowerSelector />', () => {
+    it("should reset back to custom value when custom input is blurred blank", async () => {
+        const fn = jest.fn();
+        render(<PowerSelector value={25} maxValue={100} usersDefault={0} onChange={fn} />);
+
+        const input = screen.getByLabelText("Power level");
+        fireEvent.change(input, { target: { value: "" } });
+        fireEvent.blur(input);
+
+        await screen.findByDisplayValue(25);
+        expect(fn).not.toHaveBeenCalled();
+    });
+
+    it("should reset back to preset value when custom input is blurred blank", async () => {
+        const fn = jest.fn();
+        render(<PowerSelector value={50} maxValue={100} usersDefault={0} onChange={fn} />);
+
+        const select = screen.getByLabelText("Power level");
+        fireEvent.change(select, { target: { value: "SELECT_VALUE_CUSTOM" } });
+
+        const input = screen.getByLabelText("Power level");
+        fireEvent.change(input, { target: { value: "" } });
+        fireEvent.blur(input);
+
+        const option = await screen.findByText<HTMLOptionElement>("Moderator");
+        expect(option.selected).toBeTruthy();
+        expect(fn).not.toHaveBeenCalled();
+    });
+
+    it("should call onChange when custom input is blurred with a number in it", async () => {
+        const fn = jest.fn();
+        render(<PowerSelector value={25} maxValue={100} usersDefault={0} onChange={fn} powerLevelKey="key" />);
+
+        const input = screen.getByLabelText("Power level");
+        fireEvent.change(input, { target: { value: 40 } });
+        fireEvent.blur(input);
+
+        await screen.findByDisplayValue(40);
+        expect(fn).toHaveBeenCalledWith(40, "key");
+    });
+});