diff --git a/src/ol/ImageCanvas.js b/src/ol/ImageCanvas.js
index 5207014528..dde34ad47c 100644
--- a/src/ol/ImageCanvas.js
+++ b/src/ol/ImageCanvas.js
@@ -46,7 +46,7 @@ class ImageCanvas extends ImageBase {
 
     /**
      * @private
-     * @type {Error}
+     * @type {?Error}
      */
     this.error_ = null;
 
@@ -54,7 +54,7 @@ class ImageCanvas extends ImageBase {
 
   /**
    * Get any error associated with asynchronous rendering.
-   * @return {Error} Any error that occurred during rendering.
+   * @return {?Error} Any error that occurred during rendering.
    */
   getError() {
     return this.error_;
diff --git a/src/ol/PluggableMap.js b/src/ol/PluggableMap.js
index 97ed857fdb..28ad2b1f66 100644
--- a/src/ol/PluggableMap.js
+++ b/src/ol/PluggableMap.js
@@ -332,7 +332,7 @@ class PluggableMap extends BaseObject {
     this.renderer_ = null;
 
     /**
-     * @type {function(Event): void|undefined}
+     * @type {undefined|function(Event): void}
      * @private
      */
     this.handleResize_;
diff --git a/src/ol/layer/Graticule.js b/src/ol/layer/Graticule.js
index d395bc13fa..e237ac85c8 100644
--- a/src/ol/layer/Graticule.js
+++ b/src/ol/layer/Graticule.js
@@ -421,7 +421,7 @@ class Graticule extends VectorLayer {
     });
 
     /**
-     * @type {import("../extent.js").Extent}
+     * @type {?import("../extent.js").Extent}
      */
     this.renderedExtent_ = null;
 
diff --git a/src/ol/proj.js b/src/ol/proj.js
index cd0fefea0e..f64cc05a85 100644
--- a/src/ol/proj.js
+++ b/src/ol/proj.js
@@ -499,7 +499,7 @@ export function transformWithProjections(point, sourceProjection, destinationPro
 }
 
 /**
- * @type {Projection}
+ * @type {?Projection}
  */
 let userProjection = null;
 
@@ -526,7 +526,7 @@ export function clearUserProjection() {
  * Get the projection for coordinates supplied from and returned by API methods.
  * Note that this method is not yet a part of the stable API.  Support for user
  * projections is not yet complete and should be considered experimental.
- * @returns {Projection} The user projection (or null if not set).
+ * @returns {?Projection} The user projection (or null if not set).
  */
 export function getUserProjection() {
   return userProjection;
diff --git a/src/ol/renderer/canvas/TileLayer.js b/src/ol/renderer/canvas/TileLayer.js
index 23a5026f58..6eba0a2096 100644
--- a/src/ol/renderer/canvas/TileLayer.js
+++ b/src/ol/renderer/canvas/TileLayer.js
@@ -31,7 +31,7 @@ class CanvasTileLayerRenderer extends CanvasLayerRenderer {
 
     /**
      * @private
-     * @type {import("../../extent.js").Extent}
+     * @type {?import("../../extent.js").Extent}
      */
     this.renderedExtent_ = null;