diff --git a/src/plugins/platforms/drm/drm_output.cpp b/src/plugins/platforms/drm/drm_output.cpp
index 6698b53fd2..7c756fa1d2 100644
--- a/src/plugins/platforms/drm/drm_output.cpp
+++ b/src/plugins/platforms/drm/drm_output.cpp
@@ -200,6 +200,8 @@ static AbstractWaylandOutput::SubPixel drmSubPixelToKWinSubPixel(drmModeSubPixel
         return AbstractWaylandOutput::SubPixel::Vertical_RGB;
     case DRM_MODE_SUBPIXEL_VERTICAL_BGR:
         return AbstractWaylandOutput::SubPixel::Vertical_BGR;
+    default:
+        Q_UNREACHABLE();
     }
 }