diff --git a/aom/aomcx.h b/aom/aomcx.h
index 7f0f99a..2773114 100644
--- a/aom/aomcx.h
+++ b/aom/aomcx.h
@@ -264,6 +264,8 @@
 
   /*!\brief Codec control function to set visual tuning, aom_tune_metric (int)
    * parameter
+   *
+   * The default is AOM_TUNE_PSNR.
    */
   AOME_SET_TUNING = AOME_SET_ARNR_STRENGTH + 2,  // 24