diff --git a/plugins/platforms/drm/drm_backend.h b/plugins/platforms/drm/drm_backend.h
--- a/plugins/platforms/drm/drm_backend.h
+++ b/plugins/platforms/drm/drm_backend.h
@@ -76,7 +76,6 @@
     DrmBuffer *createBuffer(gbm_surface *surface);
     void present(DrmBuffer *buffer, DrmOutput *output);
 
-    QSize size() const;
     int fd() const {
         return m_fd;
     }
diff --git a/plugins/platforms/drm/drm_backend.cpp b/plugins/platforms/drm/drm_backend.cpp
--- a/plugins/platforms/drm/drm_backend.cpp
+++ b/plugins/platforms/drm/drm_backend.cpp
@@ -664,14 +664,6 @@
     }
 }
 
-QSize DrmBackend::size() const
-{
-    if (m_outputs.isEmpty()) {
-        return QSize();
-    }
-    return m_outputs.first()->size();
-}
-
 Screens *DrmBackend::createScreens(QObject *parent)
 {
     return new DrmScreens(this, parent);