diff --git a/src/modules/active-notify/activenotifymanagerinterfacev1.cpp b/src/modules/active-notify/activenotifymanagerinterfacev1.cpp
index 2fb3b5cd7..6bcae59b8 100644
--- a/src/modules/active-notify/activenotifymanagerinterfacev1.cpp
+++ b/src/modules/active-notify/activenotifymanagerinterfacev1.cpp
@@ -5,8 +5,6 @@
 
 #include "qwayland-server-treeland-active-notify-unstable-v1.h"
 
-#include <cstring>
-
 static QList<ActiveNotifyV1 *> s_notifies;
 
 struct TreelandActiveNotifyManagerInterfaceV1Private
@@ -46,11 +44,6 @@ void TreelandActiveNotifyManagerInterfaceV1Private::get_active_notify(Resource *
                                                                        uint32_t id,
                                                                        struct ::wl_resource *seat)
 {
-    if (!seat || strcmp(wl_resource_get_class(seat), "wl_seat") != 0) {
-        wl_resource_post_error(resource->handle, 0, "seat resource is NULL or not a wl_seat!");
-        return;
-    }
-
     struct wlr_seat_client *seat_client = wlr_seat_client_from_resource(seat);
     if (!seat_client) {
         wl_resource_post_error(resource->handle, 0, "seat resource is inert!");
diff --git a/src/modules/decoration/decorationmanagerinterfacev1.cpp b/src/modules/decoration/decorationmanagerinterfacev1.cpp
index 063a490f3..a1a4f025e 100644
--- a/src/modules/decoration/decorationmanagerinterfacev1.cpp
+++ b/src/modules/decoration/decorationmanagerinterfacev1.cpp
@@ -13,8 +13,6 @@
 
 #include <wtoplevelsurface.h>
 
-#include <cstring>
-
 // ---------------------------------------------------------------------------
 // Helpers
 // ---------------------------------------------------------------------------
@@ -309,13 +307,6 @@ void DecorationManagerInterfaceV1Private::get_decoration_context(Resource *resou
                                                                  uint32_t id,
                                                                  struct ::wl_resource *surface)
 {
-    if (!surface) {
-        wl_resource_post_error(resource->handle,
-                               TREELAND_DECORATION_MANAGER_V1_ERROR_INVALID_SURFACE,
-                               "surface resource is NULL!");
-        return;
-    }
-
     // The surface must be owned by the requesting client.
     if (wl_resource_get_client(surface) != resource->client()) {
         wl_resource_post_error(resource->handle,
@@ -324,13 +315,6 @@ void DecorationManagerInterfaceV1Private::get_decoration_context(Resource *resou
         return;
     }
 
-    if (strcmp(wl_resource_get_class(surface), "wl_surface") != 0) {
-        wl_resource_post_error(resource->handle,
-                               TREELAND_DECORATION_MANAGER_V1_ERROR_INVALID_SURFACE,
-                               "invalid surface!");
-        return;
-    }
-
     auto *wlrSurface = wlr_surface_from_resource(surface);
 
     // At most one active decoration context per surface.
diff --git a/src/modules/region-watch/regionwatchmanagerinterfacev1.cpp b/src/modules/region-watch/regionwatchmanagerinterfacev1.cpp
index 758cf3be0..b9ca75133 100644
--- a/src/modules/region-watch/regionwatchmanagerinterfacev1.cpp
+++ b/src/modules/region-watch/regionwatchmanagerinterfacev1.cpp
@@ -9,8 +9,6 @@
 
 #include <QTimer>
 
-#include <string.h>
-
 #include <wayland-server.h>
 #include <wlr/types/wlr_output.h>
 
@@ -120,18 +118,6 @@ void RegionWatchV1Private::set_region(Resource *resource,
         return;
     }
 
-    // wlr_output_from_resource() asserts that the resource is a genuine
-    // wl_output; a client may pass any live object id (or an inert one),
-    // which would abort the compositor before the checks below. Validate
-    // the object class first and route invalid references to the error path.
-    if (!outputResource
-        || strcmp(wl_resource_get_class(outputResource), wl_output_interface.name) != 0) {
-        wl_resource_post_error(resource->handle,
-                               InvalidAnchor,
-                               "set_region requires a valid wl_output resource");
-        return;
-    }
-
     struct wlr_output *output = wlr_output_from_resource(outputResource);
     auto *wOutput = output ? WOutput::fromHandle(output) : nullptr;
     if (!wOutput) {
diff --git a/src/modules/xwindow-control/xwindowcontrolinterfacev1.cpp b/src/modules/xwindow-control/xwindowcontrolinterfacev1.cpp
index 14227636b..1e2dc69ab 100644
--- a/src/modules/xwindow-control/xwindowcontrolinterfacev1.cpp
+++ b/src/modules/xwindow-control/xwindowcontrolinterfacev1.cpp
@@ -11,8 +11,6 @@
 
 #include <wayland-server-core.h>
 
-#include <cstring>
-
 class XWindowControlInterfaceV1Private : public QtWaylandServer::treeland_xwindow_control_v1
 {
 public:
@@ -50,9 +48,8 @@ void XWindowControlInterfaceV1Private::set_xwindow_position_relative(Resource *r
                                                                       wl_fixed_t dx,
                                                                       wl_fixed_t dy)
 {
-    WSurface *wsurface = nullptr;
-    if (anchor && strcmp(wl_resource_get_class(anchor), "wl_surface") == 0)
-        wsurface = WSurface::fromHandle(wlr_surface_from_resource(anchor));
+    // libwayland dispatch already guarantees a genuine wl_surface.
+    auto *wsurface = WSurface::fromHandle(wlr_surface_from_resource(anchor));
     uint32_t ok = (wsurface && Helper::instance()->setXWindowPositionRelative(wid, wsurface, dx, dy)) ? 0 : 1;
     wl_resource *cb = wl_resource_create(resource->client(), &wl_callback_interface, 1, callback);
     if (!cb) {