diff --git a/include/hardware/overlay.h b/include/hardware/overlay.h
index a8287bb..eca4d27 100644
--- a/include/hardware/overlay.h
+++ b/include/hardware/overlay.h
@@ -50,7 +50,9 @@
     OVERLAY_FORMAT_YCbYCr_422_I = HAL_PIXEL_FORMAT_YCbCr_422_I,
     OVERLAY_FORMAT_YCbYCr_420_I = HAL_PIXEL_FORMAT_YCbCr_420_I,
     OVERLAY_FORMAT_CbYCrY_422_I = HAL_PIXEL_FORMAT_CbYCrY_422_I,
-    OVERLAY_FORMAT_CbYCrY_420_I = HAL_PIXEL_FORMAT_CbYCrY_420_I
+    OVERLAY_FORMAT_CbYCrY_420_I = HAL_PIXEL_FORMAT_CbYCrY_420_I,
+    OVERLAY_FORMAT_DEFAULT      = 99    // The actual color format is determined
+                                        // by the overlay
 };
 
 /* values for copybit_set_parameter(OVERLAY_TRANSFORM) */