diff --git a/lib/OpenLayers/Format/OWSContext/v0_3_1.js b/lib/OpenLayers/Format/OWSContext/v0_3_1.js
index 4f4948fbc4..afea5a88bc 100644
--- a/lib/OpenLayers/Format/OWSContext/v0_3_1.js
+++ b/lib/OpenLayers/Format/OWSContext/v0_3_1.js
@@ -466,7 +466,7 @@ OpenLayers.Format.OWSContext.v0_3_1 = OpenLayers.Class(OpenLayers.Format.XML, {
                     name: layer.params.LAYERS,
                     queryable: layer.queryable ? "1" : "0",
                     hidden: layer.visibility ? "0" : "1",
-                    opacity: layer.opacity ? layer.opacity: null}
+                    opacity: layer.hasOwnProperty("opacity") ? layer.opacity : null}
                 });
                 this.writeNode("ows:Title", layer.name, node);
                 this.writeNode("ows:OutputFormat", layer.params.FORMAT, node);
diff --git a/lib/OpenLayers/Format/WMC.js b/lib/OpenLayers/Format/WMC.js
index 8b3ad62a58..11894d3410 100644
--- a/lib/OpenLayers/Format/WMC.js
+++ b/lib/OpenLayers/Format/WMC.js
@@ -61,7 +61,7 @@ OpenLayers.Format.WMC = OpenLayers.Class(OpenLayers.Format.Context, {
             numZoomLevels: layer.numZoomLevels,
             units: layer.units,
             isBaseLayer: layer.isBaseLayer,
-            opacity: layer.opacity,
+            opacity: layer.opacity == 1 ? undefined : layer.opacity,
             displayInLayerSwitcher: layer.displayInLayerSwitcher,
             singleTile: layer.singleTile,
             tileSize: (layer.singleTile || !layer.tileSize) ? 
diff --git a/lib/OpenLayers/Layer.js b/lib/OpenLayers/Layer.js
index 763e3800a0..dca417b11c 100644
--- a/lib/OpenLayers/Layer.js
+++ b/lib/OpenLayers/Layer.js
@@ -35,9 +35,10 @@ OpenLayers.Layer = OpenLayers.Class({
 
     /**
      * Property: opacity
-     * {Float} The layer's opacity. Float number between 0.0 and 1.0.
+     * {Float} The layer's opacity. Float number between 0.0 and 1.0. Default
+     * is 1.
      */
-    opacity: null,
+    opacity: 1,
 
     /**
      * APIProperty: alwaysInRange
@@ -349,7 +350,7 @@ OpenLayers.Layer = OpenLayers.Class({
             this.div.style.width = "100%";
             this.div.style.height = "100%";
             this.div.dir = "ltr";
-            if (this.opacity != null) {
+            if (this.opacity != null && this.opacity < 1) {
                 OpenLayers.Util.modifyDOMElement(
                     this.div, null, null, null, null, null, null, this.opacity
                 );