diff --git a/src/ol/Feature.js b/src/ol/Feature.js
index 8cab579b20..d03b5905cf 100644
--- a/src/ol/Feature.js
+++ b/src/ol/Feature.js
@@ -54,7 +54,7 @@ import Style from './style/Style.js';
  */
 class Feature extends BaseObject {
   /**
-   * @param {import("./geom/Geometry.js").default|Object<string, *>=} opt_geometryOrProperties
+   * @param {Geometry|Object<string, *>=} opt_geometryOrProperties
    *     You may pass a Geometry object directly, or an object literal containing
    *     properties. If you pass an object literal, you may include a Geometry
    *     associated with a `geometry` key.
@@ -78,7 +78,7 @@ class Feature extends BaseObject {
     /**
      * User provided style.
      * @private
-     * @type {import("./style/Style.js").default|Array<import("./style/Style.js").default>|import("./style/Style.js").StyleFunction}
+     * @type {Style|Array<Style>|import("./style/Style.js").StyleFunction}
      */
     this.style_ = null;
 
@@ -99,10 +99,9 @@ class Feature extends BaseObject {
       this.handleGeometryChanged_, this);
 
     if (opt_geometryOrProperties !== undefined) {
-      if (opt_geometryOrProperties instanceof Geometry ||
-          !opt_geometryOrProperties) {
-        /** @type {?Geometry} */
-        const geometry = opt_geometryOrProperties;
+      if (opt_geometryOrProperties instanceof Geometry) {
+
+        const geometry = /** @type {Geometry} */ (opt_geometryOrProperties);
         this.setGeometry(geometry);
       } else {
         /** @type {Object<string, *>} */
@@ -136,13 +135,13 @@ class Feature extends BaseObject {
    * Get the feature's default geometry.  A feature may have any number of named
    * geometries.  The "default" geometry (the one that is rendered by default) is
    * set when calling {@link module:ol/Feature~Feature#setGeometry}.
-   * @return {import("./geom/Geometry.js").default|undefined} The default geometry for the feature.
+   * @return {Geometry|undefined} The default geometry for the feature.
    * @api
    * @observable
    */
   getGeometry() {
     return (
-      /** @type {import("./geom/Geometry.js").default|undefined} */ (this.get(this.geometryName_))
+      /** @type {Geometry|undefined} */ (this.get(this.geometryName_))
     );
   }
 
@@ -171,7 +170,7 @@ class Feature extends BaseObject {
   /**
    * Get the feature's style. Will return what was provided to the
    * {@link module:ol/Feature~Feature#setStyle} method.
-   * @return {import("./style/Style.js").default|Array<import("./style/Style.js").default>|import("./style/Style.js").StyleFunction} The feature style.
+   * @return {Style|Array<Style>|import("./style/Style.js").StyleFunction} The feature style.
    * @api
    */
   getStyle() {
@@ -214,7 +213,7 @@ class Feature extends BaseObject {
   /**
    * Set the default geometry for the feature.  This will update the property
    * with the name returned by {@link module:ol/Feature~Feature#getGeometryName}.
-   * @param {import("./geom/Geometry.js").default|undefined} geometry The new geometry.
+   * @param {Geometry|undefined} geometry The new geometry.
    * @api
    * @observable
    */
@@ -226,7 +225,7 @@ class Feature extends BaseObject {
    * Set the style for the feature.  This can be a single style object, an array
    * of styles, or a function that takes a resolution and returns an array of
    * styles. If it is `null` the feature has no style (a `null` style).
-   * @param {import("./style/Style.js").default|Array<import("./style/Style.js").default>|import("./style/Style.js").StyleFunction} style Style for this feature.
+   * @param {Style|Array<Style>|import("./style/Style.js").StyleFunction} style Style for this feature.
    * @api
    * @fires module:ol/events/Event~Event#event:change
    */
@@ -272,9 +271,9 @@ class Feature extends BaseObject {
 
 /**
  * Convert the provided object into a feature style function.  Functions passed
- * through unchanged.  Arrays of import("./style/Style.js").default or single style objects wrapped
+ * through unchanged.  Arrays of Style or single style objects wrapped
  * in a new feature style function.
- * @param {import("./style/Style.js").StyleFunction|!Array<import("./style/Style.js").default>|!import("./style/Style.js").default} obj
+ * @param {import("./style/Style.js").StyleFunction|!Array<Style>|!Style} obj
  *     A feature style function, a single style, or an array of styles.
  * @return {import("./style/Style.js").StyleFunction} A style function.
  */
@@ -283,7 +282,7 @@ export function createStyleFunction(obj) {
     return obj;
   } else {
     /**
-     * @type {Array<import("./style/Style.js").default>}
+     * @type {Array<Style>}
      */
     let styles;
     if (Array.isArray(obj)) {
diff --git a/src/ol/Geolocation.js b/src/ol/Geolocation.js
index f58127ddb3..2cac07da18 100644
--- a/src/ol/Geolocation.js
+++ b/src/ol/Geolocation.js
@@ -174,9 +174,12 @@ class Geolocation extends BaseObject {
    * @param {PositionError} error error object.
    */
   positionError_(error) {
-    error.type = EventType.ERROR;
+    const event = {
+      type: EventType.ERROR,
+      target: undefined
+    };
     this.setTracking(false);
-    this.dispatchEvent(/** @type {{type: string, target: undefined}} */ (error));
+    this.dispatchEvent(event);
   }
 
   /**
diff --git a/src/ol/ImageTile.js b/src/ol/ImageTile.js
index dcf604787c..bb172b07e6 100644
--- a/src/ol/ImageTile.js
+++ b/src/ol/ImageTile.js
@@ -114,7 +114,8 @@ class ImageTile extends Tile {
    * @private
    */
   handleImageLoad_() {
-    if (this.image_.naturalWidth && this.image_.naturalHeight) {
+    if (this.image_ instanceof HTMLImageElement &&
+      this.image_.naturalWidth && this.image_.naturalHeight) {
       this.state = TileState.LOADED;
     } else {
       this.state = TileState.EMPTY;
diff --git a/src/ol/MapBrowserEventHandler.js b/src/ol/MapBrowserEventHandler.js
index 4659e66579..b056157ee7 100644
--- a/src/ol/MapBrowserEventHandler.js
+++ b/src/ol/MapBrowserEventHandler.js
@@ -127,7 +127,7 @@ class MapBrowserEventHandler extends EventTarget {
       this.dispatchEvent(newEvent);
     } else {
       // click
-      this.clickTimeoutId_ = setTimeout(function() {
+      this.clickTimeoutId_ = window.setTimeout(function() {
         this.clickTimeoutId_ = 0;
         const newEvent = new MapBrowserPointerEvent(
           MapBrowserEventType.SINGLECLICK, this.map_, pointerEvent);
diff --git a/src/ol/geom/Geometry.js b/src/ol/geom/Geometry.js
index 887602fba3..db0f44d270 100644
--- a/src/ol/geom/Geometry.js
+++ b/src/ol/geom/Geometry.js
@@ -235,11 +235,12 @@ class Geometry extends BaseObject {
    * @api
    */
   transform(source, destination) {
-    source = getProjection(source);
-    const transformFn = source.getUnits() == Units.TILE_PIXELS ?
+    /** @type {import("../proj/Projection.js").default} */
+    const sourceProj = getProjection(source);
+    const transformFn = sourceProj.getUnits() == Units.TILE_PIXELS ?
       function(inCoordinates, outCoordinates, stride) {
-        const pixelExtent = source.getExtent();
-        const projectedExtent = source.getWorldExtent();
+        const pixelExtent = sourceProj.getExtent();
+        const projectedExtent = sourceProj.getWorldExtent();
         const scale = getHeight(projectedExtent) / getHeight(pixelExtent);
         composeTransform(tmpTransform,
           projectedExtent[0], projectedExtent[3],
@@ -247,12 +248,13 @@ class Geometry extends BaseObject {
           0, 0);
         transform2D(inCoordinates, 0, inCoordinates.length, stride,
           tmpTransform, outCoordinates);
-        return getTransform(source, destination)(inCoordinates, outCoordinates, stride);
+        return getTransform(sourceProj, destination)(inCoordinates, outCoordinates, stride);
       } :
-      getTransform(source, destination);
+      getTransform(sourceProj, destination);
     this.applyTransform(transformFn);
     return this;
   }
+
 }
 
 
diff --git a/src/ol/pointer/PointerEvent.js b/src/ol/pointer/PointerEvent.js
index 11dce303c8..f5c4f15949 100644
--- a/src/ol/pointer/PointerEvent.js
+++ b/src/ol/pointer/PointerEvent.js
@@ -32,7 +32,7 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-import Event from '../events/Event.js';
+import _Event from '../events/Event.js';
 
 
 /**
@@ -42,7 +42,7 @@ import Event from '../events/Event.js';
 let HAS_BUTTONS = false;
 
 
-class PointerEvent extends Event {
+class PointerEvent extends _Event {
 
   /**
    * A class for pointer events.
diff --git a/test/spec/ol/feature.test.js b/test/spec/ol/feature.test.js
index 3e1980a7f8..16dee02871 100644
--- a/test/spec/ol/feature.test.js
+++ b/test/spec/ol/feature.test.js
@@ -102,7 +102,7 @@ describe('ol.Feature', function() {
 
     it('returns null for null geometry (constructor)', function() {
       const feature = new Feature(null);
-      expect(feature.getGeometry()).to.be(null);
+      expect(feature.getGeometry()).to.be(undefined);
     });
 
     it('returns null for null geometry (setGeometry())', function() {