diff --git a/Applications/Terminal/Terminal.cpp b/Applications/Terminal/Terminal.cpp
index 6b82ec8f8c7..12752d43b04 100644
--- a/Applications/Terminal/Terminal.cpp
+++ b/Applications/Terminal/Terminal.cpp
@@ -891,6 +891,7 @@ void Terminal::set_opacity(float opacity)
 {
     if (m_opacity == opacity)
         return;
+    window()->set_has_alpha_channel(opacity < 1);
     m_opacity = opacity;
     force_repaint();
 }
diff --git a/Applications/Terminal/main.cpp b/Applications/Terminal/main.cpp
index e7662718b61..3afb370a89b 100644
--- a/Applications/Terminal/main.cpp
+++ b/Applications/Terminal/main.cpp
@@ -116,7 +116,7 @@ int main(int argc, char** argv)
     };
 
     slider->set_range(0, 100);
-    slider->set_value(80);
+    slider->set_value(100);
 
     auto menubar = make<GMenuBar>();
 
diff --git a/LibGUI/GEventLoop.cpp b/LibGUI/GEventLoop.cpp
index ae41ad7da1f..34e06ea0c75 100644
--- a/LibGUI/GEventLoop.cpp
+++ b/LibGUI/GEventLoop.cpp
@@ -376,6 +376,9 @@ bool GEventLoop::wait_for_specific_event(WSAPI_ServerMessage::Type type, WSAPI_S
         FD_ZERO(&rfds);
         FD_SET(s_event_fd, &rfds);
         int rc = select(s_event_fd + 1, &rfds, nullptr, nullptr, nullptr);
+        if (rc < 0) {
+            perror("select");
+        }
         ASSERT(rc > 0);
         ASSERT(FD_ISSET(s_event_fd, &rfds));
         bool success = drain_messages_from_server();
diff --git a/LibGUI/GWindow.cpp b/LibGUI/GWindow.cpp
index c1384ebe976..1dff4f2f746 100644
--- a/LibGUI/GWindow.cpp
+++ b/LibGUI/GWindow.cpp
@@ -386,8 +386,23 @@ void GWindow::set_automatic_cursor_tracking_widget(GWidget* widget)
 
 void GWindow::set_has_alpha_channel(bool value)
 {
-    ASSERT(!m_window_id);
+    if (m_has_alpha_channel == value)
+        return;
     m_has_alpha_channel = value;
+    if (!m_window_id)
+        return;
+
+    m_pending_paint_event_rects.clear();
+    m_back_bitmap = nullptr;
+    m_front_bitmap = nullptr;
+
+    WSAPI_ClientMessage message;
+    message.type = WSAPI_ClientMessage::Type::SetWindowHasAlphaChannel;
+    message.window_id = m_window_id;
+    message.value = value;
+    GEventLoop::current().sync_request(message, WSAPI_ServerMessage::DidSetWindowHasAlphaChannel);
+
+    update();
 }
 
 void GWindow::set_double_buffering_enabled(bool value)
diff --git a/Servers/WindowServer/WSAPITypes.h b/Servers/WindowServer/WSAPITypes.h
index be8027c98e4..e5f3be767a2 100644
--- a/Servers/WindowServer/WSAPITypes.h
+++ b/Servers/WindowServer/WSAPITypes.h
@@ -103,6 +103,7 @@ struct WSAPI_ServerMessage {
         DidSetWindowBackingStore,
         DidSetWallpaper,
         DidGetWallpaper,
+        DidSetWindowHasAlphaChannel,
         ScreenRectChanged,
         WM_WindowRemoved,
         WM_WindowStateChanged,
@@ -218,6 +219,7 @@ struct WSAPI_ClientMessage {
         PopupMenu,
         DismissMenu,
         SetWindowIcon,
+        SetWindowHasAlphaChannel,
     };
     Type type { Invalid };
     int window_id { -1 };
diff --git a/Servers/WindowServer/WSClientConnection.cpp b/Servers/WindowServer/WSClientConnection.cpp
index b1dec3740d9..2f3514e0110 100644
--- a/Servers/WindowServer/WSClientConnection.cpp
+++ b/Servers/WindowServer/WSClientConnection.cpp
@@ -629,6 +629,24 @@ void WSClientConnection::handle_request(const WSAPISetWindowOverrideCursorReques
     window.set_override_cursor(WSCursor::create(request.cursor()));
 }
 
+void WSClientConnection::handle_request(const WSAPISetWindowHasAlphaChannelRequest& request)
+{
+    int window_id = request.window_id();
+    auto it = m_windows.find(window_id);
+    if (it == m_windows.end()) {
+        post_error("WSAPISetWindowHasAlphaChannelRequest: Bad window ID");
+        return;
+    }
+    auto& window = *(*it).value;
+    window.set_has_alpha_channel(request.value());
+
+    WSAPI_ServerMessage response;
+    response.type = WSAPI_ServerMessage::Type::DidSetWindowHasAlphaChannel;
+    response.window_id = window_id;
+    response.value = request.value();
+    post_message(response);
+}
+
 void WSClientConnection::handle_request(const WSWMAPISetActiveWindowRequest& request)
 {
     auto* client = WSClientConnection::from_client_id(request.target_client_id());
@@ -747,6 +765,8 @@ void WSClientConnection::on_request(const WSAPIClientRequest& request)
         return handle_request(static_cast<const WSAPIPopupMenuRequest&>(request));
     case WSEvent::APIDismissMenuRequest:
         return handle_request(static_cast<const WSAPIDismissMenuRequest&>(request));
+    case WSEvent::APISetWindowHasAlphaChannelRequest:
+        return handle_request(static_cast<const WSAPISetWindowHasAlphaChannelRequest&>(request));
     default:
         break;
     }
diff --git a/Servers/WindowServer/WSClientConnection.h b/Servers/WindowServer/WSClientConnection.h
index 3cd66a537e0..da5eeb94b01 100644
--- a/Servers/WindowServer/WSClientConnection.h
+++ b/Servers/WindowServer/WSClientConnection.h
@@ -77,6 +77,7 @@ private:
     void handle_request(const WSWMAPIStartWindowResizeRequest&);
     void handle_request(const WSAPIPopupMenuRequest&);
     void handle_request(const WSAPIDismissMenuRequest&);
+    void handle_request(const WSAPISetWindowHasAlphaChannelRequest&);
 
     void post_error(const String&);
 
diff --git a/Servers/WindowServer/WSEvent.h b/Servers/WindowServer/WSEvent.h
index a22dd4cb172..a7d5b21df59 100644
--- a/Servers/WindowServer/WSEvent.h
+++ b/Servers/WindowServer/WSEvent.h
@@ -60,6 +60,7 @@ public:
         APISetWallpaperRequest,
         APIGetWallpaperRequest,
         APISetWindowOverrideCursorRequest,
+        APISetWindowHasAlphaChannelRequest,
         WMAPISetActiveWindowRequest,
         WMAPISetWindowMinimizedRequest,
         WMAPIStartWindowResizeRequest,
@@ -387,6 +388,23 @@ private:
     WSStandardCursor m_cursor { WSStandardCursor::None };
 };
 
+class WSAPISetWindowHasAlphaChannelRequest final : public WSAPIClientRequest {
+public:
+    explicit WSAPISetWindowHasAlphaChannelRequest(int client_id, int window_id, bool value)
+        : WSAPIClientRequest(WSEvent::APISetWindowHasAlphaChannelRequest, client_id)
+        , m_window_id(window_id)
+        , m_value(value)
+    {
+    }
+
+    int window_id() const { return m_window_id; }
+    bool value() const { return m_value; }
+
+private:
+    int m_window_id { 0 };
+    bool m_value { 0 };
+};
+
 class WSAPISetWallpaperRequest final : public WSAPIClientRequest {
 public:
     explicit WSAPISetWallpaperRequest(int client_id, String&& wallpaper)
diff --git a/Servers/WindowServer/WSEventLoop.cpp b/Servers/WindowServer/WSEventLoop.cpp
index c69722a5f6f..89449d0e622 100644
--- a/Servers/WindowServer/WSEventLoop.cpp
+++ b/Servers/WindowServer/WSEventLoop.cpp
@@ -244,6 +244,9 @@ bool WSEventLoop::on_receive_from_client(int client_id, const WSAPI_ClientMessag
     case WSAPI_ClientMessage::Type::SetWindowOverrideCursor:
         post_event(client, make<WSAPISetWindowOverrideCursorRequest>(client_id, message.window_id, (WSStandardCursor)message.cursor.cursor));
         break;
+    case WSAPI_ClientMessage::SetWindowHasAlphaChannel:
+        post_event(client, make<WSAPISetWindowHasAlphaChannelRequest>(client_id, message.window_id, message.value));
+        break;
     case WSAPI_ClientMessage::Type::WM_SetActiveWindow:
         post_event(client, make<WSWMAPISetActiveWindowRequest>(client_id, message.wm.client_id, message.wm.window_id));
         break;