diff --git a/src/viewport.js b/src/viewport.js
index e5c4f51a..da2ce761 100644
--- a/src/viewport.js
+++ b/src/viewport.js
@@ -664,15 +664,15 @@ $.Viewport.prototype = {
         var oldBounds = this.getBounds();
         var oldZoom   = this.getZoom();
 
-        if (Math.abs(newZoom - oldZoom) < 0.00000001 ||
-                Math.abs(newBounds.width - oldBounds.width) < 0.00000001) {
+        if (oldZoom === 0 || Math.abs(newZoom / oldZoom - 1) < 0.00000001) {
+            this.zoomTo(newZoom, true);
             return this.panTo(center, immediately);
         }
 
         newBounds = newBounds.rotate(-this.getRotation());
-        var referencePoint = newBounds.getTopLeft().divide(newBounds.width)
-            .minus(oldBounds.getTopLeft().divide(oldBounds.width))
-            .divide(1 / newBounds.width - 1 / oldBounds.width);
+        var referencePoint = newBounds.getTopLeft().times(newZoom)
+            .minus(oldBounds.getTopLeft().times(oldZoom))
+            .divide(newZoom - oldZoom);
 
         return this.zoomTo(newZoom, referencePoint, immediately);
     },
diff --git a/test/modules/viewport.js b/test/modules/viewport.js
index c3618be9..f39473cf 100644
--- a/test/modules/viewport.js
+++ b/test/modules/viewport.js
@@ -587,6 +587,44 @@
         viewer.open(DZI_PATH);
     });
 
+    asyncTest('fitBounds with almost same zoom', function() {
+        var openHandler = function() {
+            var viewport = viewer.viewport;
+            var rect1 = new OpenSeadragon.Rect(0, 0, 1, 1);
+            viewport.fitBounds(rect1, true);
+            Util.assertRectangleEquals(rect1, viewport.getBounds(), 1e-6,
+                'Bounds should be ' + rect1);
+
+            // Zoom and pan
+            var rect2 = new OpenSeadragon.Rect(1, 1, 1 + 1e-8, 1 + 1e-8);
+            viewport.fitBounds(rect2);
+            Util.assertRectangleEquals(rect2, viewport.getBounds(), 1e-6,
+                'Bounds should be ' + rect2);
+            start();
+        };
+        viewer.addOnceHandler('open', openHandler);
+        viewer.open(DZI_PATH);
+    });
+
+    asyncTest('fitBounds with big rectangle', function() {
+        var openHandler = function() {
+            var viewport = viewer.viewport;
+            var rect1 = new OpenSeadragon.Rect(0, 0, 1e9, 1e9);
+            viewport.fitBounds(rect1, true);
+            Util.assertRectangleEquals(rect1, viewport.getBounds(), 1e-6,
+                'Bounds should be ' + rect1);
+
+            // Zoom and pan
+            var rect2 = new OpenSeadragon.Rect(1, 1, 2e9, 2e9);
+            viewport.fitBounds(rect2);
+            Util.assertRectangleEquals(rect2, viewport.getBounds(), 1e-6,
+                'Bounds should be ' + rect2);
+            start();
+        };
+        viewer.addOnceHandler('open', openHandler);
+        viewer.open(DZI_PATH);
+    });
+
     asyncTest('fitHorizontally', function(){
         var openHandler = function(event) {
             viewer.removeHandler('open', openHandler);