diff --git a/src/util/imagesLoader.js b/src/util/imagesLoader.js
index 99d86287b..3e90f03d6 100644
--- a/src/util/imagesLoader.js
+++ b/src/util/imagesLoader.js
@@ -2,7 +2,9 @@ import { asArray as ol_color_asArray } from 'ol/color'
 
 /** @namespace ol.ext.imageLoader
  */
-if (window.ol) window.ol.ext.imageLoader = {};
+if (window.ol && ol.ext && !ol.ext.imageLoader) {
+  ol.ext.imageLoader = {};
+}
 
 /** Helper for loading BIL-32 (Band Interleaved by Line) image
  * @param {string} src
diff --git a/src/util/input/Base.js b/src/util/input/Base.js
index ec1029e97..940b78502 100644
--- a/src/util/input/Base.js
+++ b/src/util/input/Base.js
@@ -6,7 +6,7 @@ import ol_Object from 'ol/Object'
 /** @namespace  ol.ext.input
  */
 /*global ol*/
-if (window.ol) {
+if (window.ol && ol.ext && !ol.ext.input) {
   ol.ext.input = {};
 }