diff --git a/externs/olx.js b/externs/olx.js
index b7ae6e73ea..8ffffbe3b6 100644
--- a/externs/olx.js
+++ b/externs/olx.js
@@ -3905,7 +3905,7 @@ olx.source.OSMOptions.prototype.crossOrigin;
 
 
 /**
- * Max zoom.
+ * Max zoom. Default is `19`.
  * @type {number|undefined}
  * @api
  */
diff --git a/src/ol/source/osmsource.js b/src/ol/source/osmsource.js
index 2d8e80257d..2d757c306a 100644
--- a/src/ol/source/osmsource.js
+++ b/src/ol/source/osmsource.js
@@ -37,7 +37,7 @@ ol.source.OSM = function(opt_options) {
     attributions: attributions,
     crossOrigin: crossOrigin,
     opaque: true,
-    maxZoom: options.maxZoom,
+    maxZoom: goog.isDef(options.maxZoom) ? options.maxZoom : 19,
     tileLoadFunction: options.tileLoadFunction,
     url: url
   });