diff --git a/aom/src/aom_image.c b/aom/src/aom_image.c
index 1d3b7df..c29095c 100644
--- a/aom/src/aom_image.c
+++ b/aom/src/aom_image.c
@@ -182,7 +182,9 @@
 
   /* Default viewport to entire image. (This aom_img_set_rect call always
    * succeeds.) */
-  aom_img_set_rect(img, 0, 0, d_w, d_h, border);
+  int ret = aom_img_set_rect(img, 0, 0, d_w, d_h, border);
+  assert(ret == 0);
+  (void)ret;
   return img;
 
 fail: