diff --git a/wagtail/wagtailadmin/static_src/wagtailadmin/scss/core.scss b/wagtail/wagtailadmin/static_src/wagtailadmin/scss/core.scss
index 24acc0994..d1c06e972 100644
--- a/wagtail/wagtailadmin/static_src/wagtailadmin/scss/core.scss
+++ b/wagtail/wagtailadmin/static_src/wagtailadmin/scss/core.scss
@@ -139,8 +139,12 @@ footer {
     }
 
     .actions {
-        width: 250px;
         margin-right: $grid-gutter-width / 2;
+        width: auto;
+
+        .dropdown {
+            width: 250px;
+        }
     }
 
     .meta {
@@ -165,9 +169,12 @@ footer {
     }
 
     @media screen and (max-width: $breakpoint-mobile) {
-        .actions,
-        .preview {
+        .actions {
             width: 100%;
+
+            .dropdown {
+                width: 100%;
+            }
         }
 
         .meta p {
diff --git a/wagtail/wagtailadmin/templates/wagtailadmin/pages/create.html b/wagtail/wagtailadmin/templates/wagtailadmin/pages/create.html
index 0c22a292a..22e782bef 100644
--- a/wagtail/wagtailadmin/templates/wagtailadmin/pages/create.html
+++ b/wagtail/wagtailadmin/templates/wagtailadmin/pages/create.html
@@ -41,7 +41,7 @@
                     </div>
                 </li>
 
-                <li class="preview">
+                <li class="actions preview">
                     {% trans 'Preview' as preview_label %}
                     {% if preview_modes|length > 1 %}
                         <div class="dropdown dropup dropdown-button match-width">
diff --git a/wagtail/wagtailadmin/templates/wagtailadmin/pages/edit.html b/wagtail/wagtailadmin/templates/wagtailadmin/pages/edit.html
index c27731874..c409d59d2 100644
--- a/wagtail/wagtailadmin/templates/wagtailadmin/pages/edit.html
+++ b/wagtail/wagtailadmin/templates/wagtailadmin/pages/edit.html
@@ -64,7 +64,7 @@
                     </div>
                 </li>
 
-                <li class="preview">
+                <li class="actions preview">
                     {% trans 'Preview' as preview_label %}
                     {% if preview_modes|length > 1 %}
                         <div class="dropdown dropup dropdown-button match-width">