diff --git a/layout/reftests/css-blending/background-blending-moz-element-ref.html b/layout/reftests/css-blending/background-blending-moz-element-ref.html
index 285d30194ef..70298325c45 100644
--- a/layout/reftests/css-blending/background-blending-moz-element-ref.html
+++ b/layout/reftests/css-blending/background-blending-moz-element-ref.html
@@ -9,7 +9,7 @@
 
 .c {
     height: 10px;
-    background: rgb(0,255,0,.5);
+    background: rgba(0,255,0,.5);
 }
 
 </style>
diff --git a/layout/reftests/css-blending/background-blending-moz-element.html b/layout/reftests/css-blending/background-blending-moz-element.html
index be0e93726e3..11272a70f69 100644
--- a/layout/reftests/css-blending/background-blending-moz-element.html
+++ b/layout/reftests/css-blending/background-blending-moz-element.html
@@ -12,7 +12,7 @@ div {
 }
 
 #b {
-	background: rgb(0,255,0,.5);
+	background: rgba(0,255,0,.5);
 }
 #c {
     background: -moz-element(#b);