diff --git a/wagtail/wagtailadmin/static_src/wagtailadmin/scss/layouts/page-editor.scss b/wagtail/wagtailadmin/static_src/wagtailadmin/scss/layouts/page-editor.scss
index 52ed14c621..36a8529129 100644
--- a/wagtail/wagtailadmin/static_src/wagtailadmin/scss/layouts/page-editor.scss
+++ b/wagtail/wagtailadmin/static_src/wagtailadmin/scss/layouts/page-editor.scss
@@ -284,13 +284,6 @@
             display:none;
         }
 
-        .widget-text_input input, .richtext, textarea{
-            border:0;
-            padding:0;
-            background-color:transparent;
-            max-width:1024px;
-        }
-
         .widget-admin_image_chooser{
             label{
                 display:none;
@@ -322,6 +315,20 @@
                 }
             }
         }
+
+        /*
+        Text inputs, rich text fields and textareas that are direct children of streamfield
+        should be borderless and full-width
+        */
+        .stream-member-inner > .widget-text_input > .field-content > .input > input,
+        .stream-member-inner > .field > .field-content > .input > .richtext,
+        .stream-member-inner > .field > .field-content > .input > textarea{
+            border:0;
+            padding:0;
+            background-color:transparent;
+            max-width:1024px;
+        }
+
     }
 
     /* Object controls */
diff --git a/wagtail/wagtailadmin/templates/wagtailadmin/block_forms/sequence_member.html b/wagtail/wagtailadmin/templates/wagtailadmin/block_forms/sequence_member.html
index 1d9a44566b..6e914fcdfa 100644
--- a/wagtail/wagtailadmin/templates/wagtailadmin/block_forms/sequence_member.html
+++ b/wagtail/wagtailadmin/templates/wagtailadmin/block_forms/sequence_member.html
@@ -20,7 +20,7 @@
 
     {% block header_controls %}{% endblock %}
 
-    <div class="sequence-member-inner">{{ child.render_form }}</div>
+    <div class="sequence-member-inner {% block sequence_member_inner_classes %}{% endblock %}">{{ child.render_form }}</div>
 
     {% block footer_controls %}{% endblock %}
 </li>
diff --git a/wagtail/wagtailadmin/templates/wagtailadmin/block_forms/stream_member.html b/wagtail/wagtailadmin/templates/wagtailadmin/block_forms/stream_member.html
index 9c69f01aee..89b4cfd66d 100644
--- a/wagtail/wagtailadmin/templates/wagtailadmin/block_forms/stream_member.html
+++ b/wagtail/wagtailadmin/templates/wagtailadmin/block_forms/stream_member.html
@@ -16,6 +16,8 @@
     </div>
 {% endblock %}
 
+{% block sequence_member_inner_classes %}stream-member-inner{% endblock %}
+
 {% block footer_controls %}
     {% include "wagtailadmin/block_forms/stream_menu.html" with menu_id=prefix|add:"-appendmenu" state="closed" %}
 {% endblock %}