diff --git a/background/settings.ts b/background/settings.ts
index 51ee8bf5a..340fa5051 100644
--- a/background/settings.ts
+++ b/background/settings.ts
@@ -254,7 +254,7 @@ Object.assign<typeof updateHooks_, { [key in SettingsNS.DeclaredUpdateHooks]: Se
       const map = extAllowList_
       map.forEach((v, k): void => { v !== false && map.delete(k) })
       if (!val) { return; }
-      for (let arr = val.split("\n"), i = arr.length, wordCharRe = /^[\da-z_]/i as RegExpI; 0 <= --i; ) {
+      for (let arr = val.split("\n"), i = arr.length, wordCharRe = /^[\da-z_{]/i as RegExpI; 0 <= --i; ) {
         if ((val = arr[i].trim()) && wordCharRe.test(val)) {
           map.set(val, true)
         }
diff --git a/pages/options.html b/pages/options.html
index cf1eb936e..8b3a82b37 100644
--- a/pages/options.html
+++ b/pages/options.html
@@ -716,10 +716,9 @@
           </td>
           <td class="help"><div class="help-inner">
             <div data-i="92">Only extensions in this list are allowed to request Vimium C's support.
-            One extension id per line.</div>
-            <span data-i="93">Any line the first char of which is neither a letter nor a number or
-              "</span><kbd>_</kbd><span data-i="94">" will be ignored</span><span
-                data-i="period">.</span><span data-i="NS">
+            One extension ID per line.</div>
+            <span data-i="93">Valid extension IDs have to start with the regex <kbd>[\da-z_{]</kbd>
+              <span data-i="94"></span><span data-i="period">.</span><span data-i="NS">
             </span><a class="wrap-left-space" data-auto-resize="extAllowList" role="button" tabindex="0"
                 data-i="autoResize">Auto resize</a><span data-i="period">.</span><br>
             <a href="#" data-vim-url="vimium://wiki/Inject-into-other-extensions" data-i="95">