diff --git a/drm/DrmMode.cpp b/drm/DrmMode.cpp
index 7cbea44..d9fdb37 100644
--- a/drm/DrmMode.cpp
+++ b/drm/DrmMode.cpp
@@ -28,6 +28,11 @@
   return memcmp(&m, &mode_, offsetof(drmModeModeInfo, name)) == 0;
 }
 
+bool DrmMode::SameSize(const DrmMode &mode) const {
+  return (mode_.vdisplay == mode.mode_.vdisplay) &&
+         (mode_.hdisplay == mode.mode_.hdisplay);
+}
+
 auto DrmMode::CreateModeBlob(const DrmDevice &drm)
     -> DrmModeUserPropertyBlobUnique {
   struct drm_mode_modeinfo drm_mode = {};