diff --git a/app/assets/stylesheets/views/webauthn.scss b/app/assets/stylesheets/views/webauthn.scss
index 7f47049b0..2afc6e3fc 100644
--- a/app/assets/stylesheets/views/webauthn.scss
+++ b/app/assets/stylesheets/views/webauthn.scss
@@ -27,9 +27,12 @@
 .webauthn-illustration {
 
   @include media-down(mobile) {
-    margin: govuk-spacing(6) govuk-spacing(9) 0 govuk-spacing(9);
+    box-sizing: border-box;
+    margin: govuk-spacing(6) auto 0 auto;
+    padding: 0 govuk-spacing(9) 0 govuk-spacing(9);
   }
 
+  width: 100%;
   margin: govuk-spacing(9) auto 0 auto;
 
 }
diff --git a/app/templates/views/two-factor-webauthn.html b/app/templates/views/two-factor-webauthn.html
index fe311c3e8..08bfb63b7 100644
--- a/app/templates/views/two-factor-webauthn.html
+++ b/app/templates/views/two-factor-webauthn.html
@@ -65,7 +65,7 @@
       }) }}
     </div>
     <div class="govuk-grid-column-one-quarter">
-      <img src="{{ asset_url('images/security-key.svg') }}" alt="" class="webauthn-illustration">
+      <img src="{{ asset_url('images/security-key.svg') }}" alt="" class="webauthn-illustration" width="149" height="150">
     </div>
   </div>
 {% endblock %}
diff --git a/app/templates/views/user-profile/security-keys.html b/app/templates/views/user-profile/security-keys.html
index 3026156a4..612a9d8ee 100644
--- a/app/templates/views/user-profile/security-keys.html
+++ b/app/templates/views/user-profile/security-keys.html
@@ -99,7 +99,7 @@
         {{ webauthn_button }}
       </div>
       <div class="govuk-grid-column-one-quarter">
-        <img src="{{ asset_url('images/security-key.svg') }}" alt="" class="webauthn-illustration">
+        <img src="{{ asset_url('images/security-key.svg') }}" alt="" class="webauthn-illustration" width="149" height="150">>
       </div>
       {% endif %}
     </div>