diff --git a/lib/OpenLayers/Layer/WMS.js b/lib/OpenLayers/Layer/WMS.js
index efe39aadf2..0e87d27d52 100644
--- a/lib/OpenLayers/Layer/WMS.js
+++ b/lib/OpenLayers/Layer/WMS.js
@@ -47,7 +47,8 @@ OpenLayers.Layer.WMS.prototype =
         // unless explicitly set in options, if the layer is transparent, 
         // it will be an overlay
         if (options == null || options.isBaseLayer == null) {
-            this.isBaseLayer = ((this.params.TRANSPARENT != "true") && 
+            this.isBaseLayer = ((this.params.TRANSPARENT != "TRUE") && 
+                                (this.params.TRANSPARENT != "true") && 
                                 (this.params.TRANSPARENT != true));
         }
     },    
diff --git a/lib/OpenLayers/Layer/WMS/Untiled.js b/lib/OpenLayers/Layer/WMS/Untiled.js
index 04ab36fccd..2223083b25 100644
--- a/lib/OpenLayers/Layer/WMS/Untiled.js
+++ b/lib/OpenLayers/Layer/WMS/Untiled.js
@@ -57,7 +57,8 @@ OpenLayers.Layer.WMS.Untiled.prototype =
         // unless explicitly set in options, if the layer is transparent, 
         // it will be an overlay        
         if ((options == null) || (options.isBaseLayer == null)) {
-            this.isBaseLayer = ((this.params.TRANSPARENT != "true") && 
+            this.isBaseLayer = ((this.params.TRANSPARENT != "TRUE") && 
+                                (this.params.TRANSPARENT != "true") && 
                                 (this.params.TRANSPARENT != true));
         }
     },    
diff --git a/tests/Layer/test_WMS.html b/tests/Layer/test_WMS.html
index 2a7588a7a1..1101e5dc71 100644
--- a/tests/Layer/test_WMS.html
+++ b/tests/Layer/test_WMS.html
@@ -13,7 +13,7 @@
                    format: 'image/png'};
 
     function test_01_Layer_WMS_constructor (t) {
-        t.plan( 4 );
+        t.plan( 10 );
 
         var url = "http://octo.metacarta.com/cgi-bin/mapserv";
         layer = new OpenLayers.Layer.WMS(name, url, params);
@@ -23,7 +23,27 @@
 
         t.eq( layer.params.SERVICE, "WMS", "default params correclty uppercased and copied");
 
+        t.eq(layer.isBaseLayer, true, "no transparency setting, wms is baselayer");
 
+        params.TRANSPARENT = "true";
+        var layer2 = new OpenLayers.Layer.WMS(name, url, params);
+        t.eq(layer2.isBaseLayer, false, "transparency == 'true', wms is baselayer");
+
+        params.TRANSPARENT = "TRUE";
+        var layer3 = new OpenLayers.Layer.WMS(name, url, params);
+        t.eq(layer3.isBaseLayer, false, "transparency == 'TRUE', wms is baselayer");
+
+        params.TRANSPARENT = "TRuE";
+        var layer4 = new OpenLayers.Layer.WMS(name, url, params);
+        t.eq(layer4.isBaseLayer, true, "transparency == 'TRuE', wms is not baselayer");
+
+        params.TRANSPARENT = true;
+        var layer5 = new OpenLayers.Layer.WMS(name, url, params);
+        t.eq(layer5.isBaseLayer, false, "transparency == true, wms is baselayer");
+
+        params.TRANSPARENT = false;
+        var layer6 = new OpenLayers.Layer.WMS(name, url, params);
+        t.eq(layer6.isBaseLayer, true, "transparency == false, wms is not baselayer");
     }
     
     function test_02_Layer_WMS_addtile (t) {