diff --git a/src/imagetilesource.js b/src/imagetilesource.js
index d8d2a6d9..da1c201b 100644
--- a/src/imagetilesource.js
+++ b/src/imagetilesource.js
@@ -196,16 +196,11 @@
             return context;
         },
         /**
-         * 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).
+         * Destroys ImageTileSource
          * @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;
-            }
+        destroy: function () {
+            this._freeupCanvasMemory();
         },
 
         // private
@@ -270,7 +265,19 @@
                 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 5ce151eb..d85f5ee6 100644
--- a/src/tilesource.js
+++ b/src/tilesource.js
@@ -615,17 +615,7 @@ $.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 4653df98..93217150 100644
--- a/src/viewer.js
+++ b/src/viewer.js
@@ -742,7 +742,10 @@ $.extend( $.Viewer.prototype, $.EventSource.prototype, $.ControlDock.prototype,
             return;
         }
 
-        this.source.destroy();
+        //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.close();