--- a/image/DrawResult.h
+++ b/image/DrawResult.h
@@ -40,17 +40,17 @@ namespace image {
  * TEMPORARY_ERROR: We failed to draw due to a temporary error. Drawing may
  * succeed at a later time.
  *
  * BAD_IMAGE: We failed to draw because the image has an error. This is a
  * permanent condition.
  *
  * BAD_ARGS: We failed to draw because bad arguments were passed to draw().
  */
-enum class DrawResult : uint8_t
+enum class MOZ_MUST_USE DrawResult : uint8_t
 {
   SUCCESS,
   INCOMPLETE,
   WRONG_SIZE,
   NOT_READY,
   TEMPORARY_ERROR,
   BAD_IMAGE,
   BAD_ARGS