diff --git a/src/ol/control/attribution.js b/src/ol/control/attribution.js
index 573d0e48d4..61d4b2fe0d 100644
--- a/src/ol/control/attribution.js
+++ b/src/ol/control/attribution.js
@@ -217,15 +217,8 @@ ol.control.Attribution.prototype.getLayerAttributionVisiblities_ =
       if (store instanceof ol.TileStore) {
         attributionVisible = goog.array.some(
             coverageAreas,
-            /**
-             * @param {ol.TileCoverageArea} tileCoverageArea
-             *     Tile coverage area.
-             * @param {number} index Index.
-             */
-            function(tileCoverageArea, index) {
-              goog.asserts.assert(
-                  tileCoverageArea instanceof ol.TileCoverageArea);
-              return tileCoverageArea.intersectsExtentAndZ(mapExtent, mapZ);
+            function(coverageArea, index) {
+              return coverageArea.intersectsExtentAndZ(mapExtent, mapZ);
             });
       } else {
         attributionVisible = goog.array.some(
diff --git a/src/ol/coveragearea.js b/src/ol/coveragearea.js
index 491028e7cb..e41f834381 100644
--- a/src/ol/coveragearea.js
+++ b/src/ol/coveragearea.js
@@ -35,6 +35,14 @@ ol.CoverageArea.prototype.intersectsExtent = function(extent) {
 ol.CoverageArea.prototype.intersectsExtentAndResolution = goog.abstractMethod;
 
 
+/**
+ * @param {ol.Extent} extent Extent.
+ * @param {number} z Z.
+ * @return {boolean} Intersects.
+ */
+ol.CoverageArea.prototype.intersectsExtentAndZ = goog.abstractMethod;
+
+
 /**
  * @param {ol.TransformFunction} transformFn Transform.
  * @return {ol.CoverageArea} Transformed coverage area.
diff --git a/src/ol/tilecoveragearea.js b/src/ol/tilecoveragearea.js
index 5ca7e2fabe..d6284ec450 100644
--- a/src/ol/tilecoveragearea.js
+++ b/src/ol/tilecoveragearea.js
@@ -51,9 +51,7 @@ ol.TileCoverageArea.prototype.intersectsExtentAndResolution =
 
 
 /**
- * @param {ol.Extent} extent Extent.
- * @param {number} z Z.
- * @return {boolean} Intersects.
+ * @inheritDoc
  */
 ol.TileCoverageArea.prototype.intersectsExtentAndZ = function(extent, z) {
   return this.minZ_ <= z && z <= this.maxZ_ && this.intersectsExtent(extent);