diff --git a/src/ol/format/mvt.js b/src/ol/format/mvt.js
index 64d113bbce..5b83304ab8 100644
--- a/src/ol/format/mvt.js
+++ b/src/ol/format/mvt.js
@@ -256,40 +256,35 @@ ol.format.MVT.readGeometry_ = function(rawFeature) {
 
 
 /**
+ * Not implemented.
  * @override
  */
-ol.format.MVT.prototype.readFeature = function() {
-  throw new Error('Not implemented');
-};
+ol.format.MVT.prototype.readFeature = function() {};
 
 
 /**
+ * Not implemented.
  * @override
  */
-ol.format.MVT.prototype.readGeometry = function() {
-  throw new Error('Not implemented');
-};
+ol.format.MVT.prototype.readGeometry = function() {};
 
 
 /**
+ * Not implemented.
  * @override
  */
-ol.format.MVT.prototype.writeFeature = function() {
-  throw new Error('Not implemented');
-};
+ol.format.MVT.prototype.writeFeature = function() {};
 
 
 /**
+ * Not implemented.
  * @override
  */
-ol.format.MVT.prototype.writeGeometry = function() {
-  throw new Error('Not implemented');
-};
+ol.format.MVT.prototype.writeGeometry = function() {};
 
 
 /**
+ * Not implemented.
  * @override
  */
-ol.format.MVT.prototype.writeFeatures = function() {
-  throw new Error('Not implemented');
-};
+ol.format.MVT.prototype.writeFeatures = function() {};
diff --git a/src/ol/format/topojson.js b/src/ol/format/topojson.js
index 97d23bc240..34ea6874cc 100644
--- a/src/ol/format/topojson.js
+++ b/src/ol/format/topojson.js
@@ -419,16 +419,14 @@ ol.format.TopoJSON.prototype.writeGeometryObject = function(geometry, opt_option
 
 
 /**
+ * Not implemented.
  * @override
  */
-ol.format.TopoJSON.prototype.readGeometryFromObject = function() {
-  throw new Error('Not implemented');
-};
+ol.format.TopoJSON.prototype.readGeometryFromObject = function() {};
 
 
 /**
+ * Not implemented.
  * @override
  */
-ol.format.TopoJSON.prototype.readFeatureFromObject = function() {
-  throw new Error('Not implemented');
-};
+ol.format.TopoJSON.prototype.readFeatureFromObject = function() {};
diff --git a/src/ol/format/xmlfeature.js b/src/ol/format/xmlfeature.js
index ec57f14c3f..5a67c551bc 100644
--- a/src/ol/format/xmlfeature.js
+++ b/src/ol/format/xmlfeature.js
@@ -7,9 +7,6 @@ goog.require('ol.format.FormatType');
 goog.require('ol.xml');
 
 
-/* eslint-disable valid-jsdoc */
-
-
 /**
  * @classdesc
  * Abstract base class; normally only used for creating subclasses and not
@@ -81,7 +78,7 @@ ol.format.XMLFeature.prototype.readFeatureFromDocument = function(
  * @return {ol.Feature} Feature.
  */
 ol.format.XMLFeature.prototype.readFeatureFromNode = function(node, opt_options) {
-  throw new Error('Not implemented');
+  return null; // not implemented
 };
 
 
@@ -158,7 +155,7 @@ ol.format.XMLFeature.prototype.readGeometry = function(source, opt_options) {
  * @return {ol.geom.Geometry} Geometry.
  */
 ol.format.XMLFeature.prototype.readGeometryFromDocument = function(doc, opt_options) {
-  throw new Error('Not implemented');
+  return null; // not implemented
 };
 
 
@@ -169,7 +166,7 @@ ol.format.XMLFeature.prototype.readGeometryFromDocument = function(doc, opt_opti
  * @return {ol.geom.Geometry} Geometry.
  */
 ol.format.XMLFeature.prototype.readGeometryFromNode = function(node, opt_options) {
-  throw new Error('Not implemented');
+  return null; // not implemented
 };
 
 
@@ -226,7 +223,7 @@ ol.format.XMLFeature.prototype.writeFeature = function(feature, opt_options) {
  * @return {Node} Node.
  */
 ol.format.XMLFeature.prototype.writeFeatureNode = function(feature, opt_options) {
-  throw new Error('Not implemented');
+  return null; // not implemented
 };
 
 
@@ -245,7 +242,7 @@ ol.format.XMLFeature.prototype.writeFeatures = function(features, opt_options) {
  * @return {Node} Node.
  */
 ol.format.XMLFeature.prototype.writeFeaturesNode = function(features, opt_options) {
-  throw new Error('Not implemented');
+  return null; // not implemented
 };
 
 
@@ -264,5 +261,5 @@ ol.format.XMLFeature.prototype.writeGeometry = function(geometry, opt_options) {
  * @return {Node} Node.
  */
 ol.format.XMLFeature.prototype.writeGeometryNode = function(geometry, opt_options) {
-  throw new Error('Not implemented');
+  return null; // not implemented
 };
diff --git a/src/ol/source/raster.js b/src/ol/source/raster.js
index 0d6e95ca5f..2ebcc06937 100644
--- a/src/ol/source/raster.js
+++ b/src/ol/source/raster.js
@@ -489,7 +489,7 @@ ol.inherits(ol.source.Raster.Event, ol.events.Event);
  * @override
  */
 ol.source.Raster.prototype.getImageInternal = function() {
-  throw new Error('Not implemented');
+  return null; // not implemented
 };