diff --git a/ts/test-both/util/url_test.ts b/ts/test-both/util/url_test.ts
index bae6a684cb..e0727651c4 100644
--- a/ts/test-both/util/url_test.ts
+++ b/ts/test-both/util/url_test.ts
@@ -4,7 +4,11 @@
 import { assert } from 'chai';
 import { size } from '../../util/iterables';
 
-import { maybeParseUrl, setUrlSearchParams } from '../../util/url';
+import {
+  maybeParseUrl,
+  setUrlSearchParams,
+  urlPathFromComponents,
+} from '../../util/url';
 
 describe('URL utilities', () => {
   describe('maybeParseUrl', () => {
@@ -84,4 +88,18 @@ describe('URL utilities', () => {
       assert.strictEqual(newUrl.search, '?foo=bar');
     });
   });
+
+  describe('urlPathFromComponents', () => {
+    it('returns / if no components are provided', () => {
+      assert.strictEqual(urlPathFromComponents([]), '/');
+    });
+
+    it('joins components, percent-encoding them and removing empty components', () => {
+      const components = ['foo', '', '~', 'bar / baz qúx'];
+      assert.strictEqual(
+        urlPathFromComponents(components),
+        '/foo/~/bar%20%2F%20baz%20q%C3%BAx'
+      );
+    });
+  });
 });
diff --git a/ts/textsecure/WebAPI.ts b/ts/textsecure/WebAPI.ts
index 61d016fb3b..c0f8746518 100644
--- a/ts/textsecure/WebAPI.ts
+++ b/ts/textsecure/WebAPI.ts
@@ -54,7 +54,7 @@ import type {
 } from './Types.d';
 import { handleStatusCode, translateError } from './Utils';
 import * as log from '../logging/log';
-import { maybeParseUrl } from '../util/url';
+import { maybeParseUrl, urlPathFromComponents } from '../util/url';
 
 // Note: this will break some code that expects to be able to use err.response when a
 //   web request fails, because it will force it to text. But it is very useful for
@@ -1780,7 +1780,7 @@ export function initialize({
       await _ajax({
         call: 'reportMessage',
         httpType: 'POST',
-        urlParameters: `/${senderUuid}/${serverGuid}`,
+        urlParameters: urlPathFromComponents([senderUuid, serverGuid]),
         responseType: 'bytes',
       });
     }
diff --git a/ts/util/url.ts b/ts/util/url.ts
index b214501a31..c934128d9b 100644
--- a/ts/util/url.ts
+++ b/ts/util/url.ts
@@ -33,3 +33,9 @@ function cloneUrl(url: Readonly<URL>): URL {
 function stringifySearchParamValue(value: unknown): string {
   return value == null ? '' : String(value);
 }
+
+export function urlPathFromComponents(
+  components: ReadonlyArray<string>
+): string {
+  return `/${components.filter(Boolean).map(encodeURIComponent).join('/')}`;
+}