diff --git a/gsk/gpu/gskgpucolorstatesprivate.h b/gsk/gpu/gskgpucolorstatesprivate.h
index 07ccdb8775..c761bfe84e 100644
--- a/gsk/gpu/gskgpucolorstatesprivate.h
+++ b/gsk/gpu/gskgpucolorstatesprivate.h
@@ -44,6 +44,8 @@ gsk_gpu_color_states_create_cicp (GdkColorState *output_color_state,
                                   gboolean       output_is_premultiplied,
                                   gboolean       cicp_is_premultiplied)
 {
+  g_assert (GDK_IS_DEFAULT_COLOR_STATE (output_color_state));
+
   return (GDK_DEFAULT_COLOR_STATE_ID (output_color_state) << COLOR_SPACE_OUTPUT_SHIFT) |
          (output_is_premultiplied ? COLOR_SPACE_OUTPUT_PREMULTIPLIED : 0) |
          (GDK_DEFAULT_COLOR_STATE_ID (output_color_state) << COLOR_SPACE_ALT_SHIFT) |