diff --git a/src/css.js b/src/css.js
index 79ae00e37..4bf818e5a 100644
--- a/src/css.js
+++ b/src/css.js
@@ -204,7 +204,7 @@ if ( !jQuery.support.opacity ) {
 
 			style.filter = ralpha.test(filter) ?
 				filter.replace(ralpha, opacity) :
-				opacity;
+				style.filter + ' ' + opacity;
 		}
 	};
 }
diff --git a/test/unit/css.js b/test/unit/css.js
index 8802fc00a..468f76386 100644
--- a/test/unit/css.js
+++ b/test/unit/css.js
@@ -114,11 +114,14 @@ if(jQuery.browser.msie) {
 
     var filterVal = "progid:DXImageTransform.Microsoft.Alpha(opacity=30) progid:DXImageTransform.Microsoft.Blur(pixelradius=5)";
     var filterVal2 = "progid:DXImageTransform.Microsoft.alpha(opacity=100) progid:DXImageTransform.Microsoft.Blur(pixelradius=5)";
+    var filterVal3 = "progid:DXImageTransform.Microsoft.Blur(pixelradius=5)";
     jQuery('#foo').css("filter", filterVal);
     equals( jQuery('#foo').css("filter"), filterVal, "css('filter', val) works" );
-    jQuery('#foo').css("opacity", 1)
-    equals( jQuery('#foo').css("filter"), filterVal2, "Setting opacity in IE doesn't clobber other filters" );
-    equals( jQuery('#foo').css("opacity"), 1, "Setting opacity in IE with other filters works" )
+    jQuery('#foo').css("opacity", 1);
+    equals( jQuery('#foo').css("filter"), filterVal2, "Setting opacity in IE doesn't duplicate opacity filter" );
+    equals( jQuery('#foo').css("opacity"), 1, "Setting opacity in IE with other filters works" );
+    jQuery('#foo').css("filter", filterVal3).css("opacity", 1);
+    ok( jQuery('#foo').css("filter").indexOf(filterVal3) !== -1, "Setting opacity in IE doesn't clobber other filters" );
   });
 }