diff --git a/src/imagetilesource.js b/src/imagetilesource.js
index da1c201b..d8d2a6d9 100644
--- a/src/imagetilesource.js
+++ b/src/imagetilesource.js
@@ -196,11 +196,16 @@
             return context;
         },
         /**
-         * Destroys ImageTileSource
+         * Free up canvas memory
+         * (iOS 12 or higher on 2GB RAM device has only 224MB canvas memory,
+         * and Safari keeps canvas until its height and width will be set to 0).
          * @function
          */
-        destroy: function () {
-            this._freeupCanvasMemory();
+        freeupCanvasMemory: function () {
+            for (var i = 0; i < this.levels.length; i++) {
+                this.levels[i].context2D.canvas.height = 0;
+                this.levels[i].context2D.canvas.width = 0;
+            }
         },
 
         // private
@@ -265,19 +270,7 @@
                 bigContext = smallContext;
             }
             return levels;
-        },
-        /**
-         * Free up canvas memory
-         * (iOS 12 or higher on 2GB RAM device has only 224MB canvas memory,
-         * and Safari keeps canvas until its height and width will be set to 0).
-         * @function
-         */
-        _freeupCanvasMemory: function () {
-            for (var i = 0; i < this.levels.length; i++) {
-                this.levels[i].context2D.canvas.height = 0;
-                this.levels[i].context2D.canvas.width = 0;
-            }
-        },
+        }
     });
 
 }(OpenSeadragon));
diff --git a/src/tilesource.js b/src/tilesource.js
index d85f5ee6..5ce151eb 100644
--- a/src/tilesource.js
+++ b/src/tilesource.js
@@ -615,7 +615,17 @@ $.TileSource.prototype = {
                y >= 0 &&
                x < numTiles.x &&
                y < numTiles.y;
-    }
+    },
+
+    /**
+     * Destroys TileSource
+     * @function
+     */
+    destroy: function () {
+        if ( this.freeupCanvasMemory ) {
+            this.freeupCanvasMemory();
+        }
+    },
 };
 
 
diff --git a/src/viewer.js b/src/viewer.js
index 93217150..4653df98 100644
--- a/src/viewer.js
+++ b/src/viewer.js
@@ -742,10 +742,7 @@ $.extend( $.Viewer.prototype, $.EventSource.prototype, $.ControlDock.prototype,
             return;
         }
 
-        //TODO: implement destroy and _freeupCanvasMemory method for all child classes of TileSource, then remove if statement wrap below.
-        if (this.source.destroy) {
-            this.source.destroy();
-        }
+        this.source.destroy();
 
         this.close();
 
diff --git a/test/demo/memorycheck-with-simple-image.html b/test/demo/memorycheck-with-simple-image.html
index c676b062..292c6994 100644
--- a/test/demo/memorycheck-with-simple-image.html
+++ b/test/demo/memorycheck-with-simple-image.html
@@ -35,6 +35,7 @@
             _viewer = OpenSeadragon({
                 element: document.getElementById("contentDiv"),
                 showNavigationControl: false,
+                prefixUrl: "../../build/openseadragon/images/",
                 tileSources: {
                     type: "image",
                     url: "../data/CCyan.png"