diff --git a/CHANGELOG b/CHANGELOG
index c76abce..c4a8583 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,5 @@
+* Coerce Opera's version string into a number whenever we need to sniff. [Sam Holman, jddalton]
+
 * Ensure Object.isElement handles "falsy" values properly. (kangax)
 
 * Fix exiting test task on INT signal. (Samuel Lebeau)
diff --git a/src/dom.js b/src/dom.js
index ce87673..07ef2d6 100644
--- a/src/dom.js
+++ b/src/dom.js
@@ -1179,8 +1179,15 @@ document.viewport = {
     var dimensions = { }, B = Prototype.Browser;
     $w('width height').each(function(d) {
       var D = d.capitalize();
-      dimensions[d] = (B.WebKit && !document.evaluate) ? self['inner' + D] :
-        (B.Opera && opera.version() < 9.5) ? document.body['client' + D] : document.documentElement['client' + D];
+      if (B.WebKit && !document.evaluate) {
+        // Safari <3.0 needs self.innerWidth/Height
+        dimensions[d] = self['inner' + D];
+      } else if (B.Opera && parseFloat(window.opera.version()) < 9.5) {
+        // Opera <9.5 needs document.body.clientWidth/Height
+        dimensions[d] = document.body['client' + D]
+      } else {
+        dimensions[d] = document.documentElement['client' + D];
+      }
     });
     return dimensions;
   },