diff --git a/core/misc/dialog/off-canvas.base.css b/core/misc/dialog/off-canvas.base.css
index f50e4e7226..138ea03a0f 100644
--- a/core/misc/dialog/off-canvas.base.css
+++ b/core/misc/dialog/off-canvas.base.css
@@ -4,7 +4,8 @@
  */
 
 /* Set some global attributes. */
-#drupal-off-canvas {
+#drupal-off-canvas *,
+#drupal-off-canvas *:not(div) {
   background: #444;
   font-family: "Lucida Grande", 'Lucida Sans Unicode', 'liberation sans', sans-serif;
   color: #ddd;
diff --git a/core/modules/workspace/css/workspace.overview.css b/core/modules/workspace/css/workspace.overview.css
index 2e42e7a1a3..2e8e812ba2 100644
--- a/core/modules/workspace/css/workspace.overview.css
+++ b/core/modules/workspace/css/workspace.overview.css
@@ -3,7 +3,7 @@
  * Styling for the Workspace overview table.
  */
 
-/** Move to Seven theme before Workspace is marked stable. */
+/** @todo Move to Seven theme before Workspace is marked stable. */
 tr.active-workspace {
   background-color: #ebeae4;
 }
diff --git a/core/modules/workspace/css/workspace.toolbar.css b/core/modules/workspace/css/workspace.toolbar.css
index 0bcb8060fe..4194a66e12 100644
--- a/core/modules/workspace/css/workspace.toolbar.css
+++ b/core/modules/workspace/css/workspace.toolbar.css
@@ -3,6 +3,18 @@
  * Styling for Workspace module's toolbar tab.
  */
 
+/**
+ * @todo Remove this after https://www.drupal.org/project/drupal/issues/2986056
+ *  has been solved.
+ */
+.workspace-dialog #drupal-off-canvas * {
+  background: initial;
+}
+.workspace-dialog #drupal-off-canvas {
+  background: #444;
+}
+
+
 /* Tab appearance. */
 .toolbar .toolbar-bar .workspace-toolbar-tab {
   float: right; /* LTR */
@@ -156,6 +168,7 @@
   left: 20px;
 }
 
+
 @media all and (min-width: 767px) {
   #drupal-off-canvas .active-workspace__label:before {
     left: 40px;
diff --git a/core/themes/stable/css/core/dialog/off-canvas.base.css b/core/themes/stable/css/core/dialog/off-canvas.base.css
index cc46bcfa30..917dd2390c 100644
--- a/core/themes/stable/css/core/dialog/off-canvas.base.css
+++ b/core/themes/stable/css/core/dialog/off-canvas.base.css
@@ -4,7 +4,8 @@
  */
 
 /* Set some global attributes. */
-#drupal-off-canvas {
+#drupal-off-canvas *,
+#drupal-off-canvas *:not(div) {
   background: #444;
   font-family: "Lucida Grande", 'Lucida Sans Unicode', 'liberation sans', sans-serif;
   color: #ddd;