diff --git a/web/src/style.css b/web/src/style.css
index 36833f3..c0c0585 100644
--- a/web/src/style.css
+++ b/web/src/style.css
@@ -765,7 +765,8 @@ h1 {
   font-size: 1rem;
 }
 
-button[type="submit"] {
+button[type="submit"],
+.btn-primary {
   padding: 0.6rem 1rem;
   border: none;
   border-radius: 8px;
@@ -775,7 +776,14 @@ button[type="submit"] {
   cursor: pointer;
 }
 
-button[type="submit"]:disabled {
+.btn-primary {
+  display: block;
+  width: 100%;
+  text-align: center;
+}
+
+button[type="submit"]:disabled,
+.btn-primary:disabled {
   opacity: 0.6;
   cursor: progress;
 }
diff --git a/web/src/views/LoginView.vue b/web/src/views/LoginView.vue
index 7aba731..8a6da79 100644
--- a/web/src/views/LoginView.vue
+++ b/web/src/views/LoginView.vue
@@ -56,7 +56,7 @@ async function onPasskeyLogin() {
     <h1>Log in</h1>
 
     <template v-if="passkeySupported">
-      <button type="button" :disabled="passkeySubmitting" @click="onPasskeyLogin">
+      <button type="button" class="btn-primary" :disabled="passkeySubmitting" @click="onPasskeyLogin">
         {{ passkeySubmitting ? 'Waiting for your passkey…' : 'Log in with a passkey' }}
       </button>
       <p v-if="passkeyError" class="form-error">{{ passkeyError }}</p>