diff --git a/gfx/2d/HelpersCairo.h b/gfx/2d/HelpersCairo.h
index 3c5b743408fa..395067b76829 100644
--- a/gfx/2d/HelpersCairo.h
+++ b/gfx/2d/HelpersCairo.h
@@ -229,8 +229,7 @@ CairoFormatToGfxFormat(cairo_format_t format)
     case CAIRO_FORMAT_RGB16_565:
       return SurfaceFormat::R5G6B5;
     default:
-      gfxWarning() << "Unknown cairo format";
-      MOZ_ASSERT(false, "Unknown cairo format");
+      gfxCriticalError() << "Unknown cairo format " << format;
       return SurfaceFormat::UNKNOWN;
   }
 }