diff --git a/src/objectliterals.jsdoc b/src/objectliterals.jsdoc
index 6c1c23e5f1..80bb5cb20a 100644
--- a/src/objectliterals.jsdoc
+++ b/src/objectliterals.jsdoc
@@ -652,7 +652,14 @@
 /**
  * @typedef {Object} olx.source.ImageCanvasOptions
  * @property {Array.<ol.Attribution>|undefined} attributions Attributions.
- * @property {ol.CanvasFunctionType} canvasFunction Canvas function.
+ * @property {ol.CanvasFunctionType} canvasFunction Canvas function. The function
+ *     returning the canvas element used by the source as an image. The arguments
+ *     passed to the function are: `{ol.Extent}` the image extent, `{number}` the
+ *     image resolution, `{number}` the device pixel ratio, `{ol.Size}` the image
+ *     size, and `{ol.proj.Projection}` the image projection. The canvas returned
+ *     by this function is cached by the source. If the value returned by the
+ *     function is later changed then `dispatchChangeEvent` should be called on
+ *     the source for the source to invalidate the current cached image.
  * @property {ol.Extent|undefined} extent Extent.
  * @property {string|undefined} logo Logo.
  * @property {ol.proj.ProjectionLike} projection Projection.