diff --git a/lib/bds/desktop/shell_live/index.html.heex b/lib/bds/desktop/shell_live/index.html.heex
index 631eb3e..b461acd 100644
--- a/lib/bds/desktop/shell_live/index.html.heex
+++ b/lib/bds/desktop/shell_live/index.html.heex
@@ -90,7 +90,7 @@
     <section
       class={["sidebar-shell", if(not @workbench.sidebar_visible, do: "is-hidden")]}
       data-testid="sidebar-shell"
-      style={"width: #{@workbench.sidebar_width}px;"}
+      style={"width: #{if(@workbench.sidebar_visible, do: @workbench.sidebar_width, else: 0)}px;"}
     >
       <div class="sidebar" data-region="sidebar">
         <div id="sidebar-content" class="sidebar-content sidebar-body" phx-hook="SidebarInteractions">
@@ -307,7 +307,7 @@
     <section
       class={["assistant-sidebar-shell", if(not @workbench.assistant_sidebar_visible, do: "is-hidden")]}
       data-testid="assistant-shell"
-      style={"width: #{@workbench.assistant_sidebar_width}px;"}
+      style={"width: #{if(@workbench.assistant_sidebar_visible, do: @workbench.assistant_sidebar_width, else: 0)}px;"}
     >
       <div class="resizable-panel-divider assistant-divider" data-resize="assistant" data-role="resize-handle"></div>
       <aside class="assistant-sidebar" data-region="assistant-sidebar">
diff --git a/test/bds/desktop/shell_live_test.exs b/test/bds/desktop/shell_live_test.exs
index 5c03dae..d58c580 100644
--- a/test/bds/desktop/shell_live_test.exs
+++ b/test/bds/desktop/shell_live_test.exs
@@ -154,4 +154,19 @@ defmodule BDS.Desktop.ShellLiveTest do
     html = render_keydown(view, "shortcut", %{key: "w", meta: true})
     refute html =~ ~s(data-tab-id="media-1")
   end
+
+  test "hiding the sidebar collapses its width to zero" do
+    {:ok, view, html} = live_isolated(build_conn(), BDS.Desktop.ShellLive)
+
+    assert html =~ ~s(data-testid="sidebar-shell")
+    assert html =~ ~s(style="width: 280px;")
+
+    html =
+      view
+      |> element("[data-testid='toggle-sidebar']")
+      |> render_click()
+
+    assert html =~ ~s(class="sidebar-shell is-hidden")
+    assert html =~ ~s(style="width: 0px;")
+  end
 end