diff --git a/src/drawer.js b/src/drawer.js
index 3055feda..2e100384 100644
--- a/src/drawer.js
+++ b/src/drawer.js
@@ -1234,6 +1234,8 @@ function drawTiles( drawer, lastDrawn ){
           /**
            * This event is fired just before the tile is drawn giving the application a chance to alter the image.
            *
+           * NOTE: This event is only fired when the drawer is using a <canvas>.
+           *
            * @event tile-drawing
            * @memberof OpenSeadragon.Viewer
            * @type {object}