diff --git a/externs/olx.js b/externs/olx.js
index 8f514094bb..64befa666a 100644
--- a/externs/olx.js
+++ b/externs/olx.js
@@ -4184,6 +4184,7 @@ olx.source.StaticVectorOptions.prototype.urls;
  *     requestEncoding: (ol.source.WMTSRequestEncoding|undefined),
  *     layer: string,
  *     style: string,
+ *     tilePixelRatio: (number|undefined),
  *     version: (string|undefined),
  *     format: (string|undefined),
  *     matrixSet: string,
@@ -4260,6 +4261,13 @@ olx.source.WMTSOptions.prototype.layer;
 olx.source.WMTSOptions.prototype.style;
 
 
+/**
+ * Tile pixel ratio.
+ * @type {number|undefined}
+ */
+olx.source.WMTSOptions.prototype.tilePixelRatio;
+
+
 /**
  * WMTS version. Default to `1.0.0`.
  * @type {string|undefined}
diff --git a/src/ol/source/wmtssource.js b/src/ol/source/wmtssource.js
index 975039994a..5eb8fe3662 100644
--- a/src/ol/source/wmtssource.js
+++ b/src/ol/source/wmtssource.js
@@ -186,6 +186,7 @@ ol.source.WMTS = function(options) {
     projection: options.projection,
     tileGrid: tileGrid,
     tileLoadFunction: options.tileLoadFunction,
+    tilePixelRatio: options.tilePixelRatio,
     tileUrlFunction: tileUrlFunction
   });