diff --git a/src/ol/control/MousePosition.js b/src/ol/control/MousePosition.js
index 680a2120a8..97684cb8e2 100644
--- a/src/ol/control/MousePosition.js
+++ b/src/ol/control/MousePosition.js
@@ -79,7 +79,7 @@ class MousePosition extends Control {
      * @private
      * @type {string}
      */
-    this.undefinedHTML_ = 'undefinedHTML' in options ? options.undefinedHTML : ' ';
+    this.undefinedHTML_ = options.undefinedHTML !== undefined ? options.undefinedHTML : ' ';
 
     /**
      * @private