diff --git a/src/stores/UIStore.ts b/src/stores/UIStore.ts
index 86312f79d7..b89af2f7c0 100644
--- a/src/stores/UIStore.ts
+++ b/src/stores/UIStore.ts
@@ -15,7 +15,11 @@ limitations under the License.
 */
 
 import EventEmitter from "events";
-import ResizeObserver from 'resize-observer-polyfill';
+// XXX: resize-observer-polyfill has types that now conflict with typescript's
+// own DOM types: https://github.com/que-etc/resize-observer-polyfill/issues/80
+// Using require here rather than import is a horrenous workaround. We should
+// be able to remove the polyfill once Safari 14 is released.
+const ResizeObserverPolyfill = require('resize-observer-polyfill'); // eslint-disable-line @typescript-eslint/no-var-requires
 import ResizeObserverEntry from 'resize-observer-polyfill/src/ResizeObserverEntry';
 
 export enum UI_EVENTS {
@@ -43,7 +47,7 @@ export default class UIStore extends EventEmitter {
         // eslint-disable-next-line no-restricted-properties
         this.windowHeight = window.innerHeight;
 
-        this.resizeObserver = new ResizeObserver(this.resizeObserverCallback);
+        this.resizeObserver = new ResizeObserverPolyfill(this.resizeObserverCallback);
         this.resizeObserver.observe(document.body);
     }
 
diff --git a/src/utils/PasswordScorer.ts b/src/utils/PasswordScorer.ts
index e3c30c1680..9aae4039bd 100644
--- a/src/utils/PasswordScorer.ts
+++ b/src/utils/PasswordScorer.ts
@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import zxcvbn from 'zxcvbn';
+import zxcvbn, { ZXCVBNFeedbackWarning } from 'zxcvbn';
 
 import { MatrixClientPeg } from '../MatrixClientPeg';
 import { _t, _td } from '../languageHandler';
@@ -84,7 +84,7 @@ export function scorePassword(password: string) {
     }
     // and warning, if any
     if (zxcvbnResult.feedback.warning) {
-        zxcvbnResult.feedback.warning = _t(zxcvbnResult.feedback.warning);
+        zxcvbnResult.feedback.warning = _t(zxcvbnResult.feedback.warning) as ZXCVBNFeedbackWarning;
     }
 
     return zxcvbnResult;