Index: trunk/src/org/openstreetmap/josm/gui/mappaint/AreaElemStyle.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/mappaint/AreaElemStyle.java	(revision 5375)
+++ trunk/src/org/openstreetmap/josm/gui/mappaint/AreaElemStyle.java	(revision 5376)
@@ -49,5 +49,5 @@
 
             fillImage.alpha = Math.min(255, Math.max(0, Integer.valueOf(Main.pref.getInteger("mappaint.fill-image-alpha", 255))));
-            Integer pAlpha = Utils.color_float2int(c.get("fill-opacity", null, float.class));
+            Integer pAlpha = Utils.color_float2int(c.get(FILL_OPACITY, null, float.class));
             if (pAlpha != null) {
                 fillImage.alpha = pAlpha;
@@ -57,5 +57,5 @@
             if (color != null) {
                 int alpha = Math.min(255, Math.max(0, Integer.valueOf(Main.pref.getInteger("mappaint.fillalpha", 50))));
-                Integer pAlpha = Utils.color_float2int(c.get("fill-opacity", null, float.class));
+                Integer pAlpha = Utils.color_float2int(c.get(FILL_OPACITY, null, float.class));
                 if (pAlpha != null) {
                     alpha = pAlpha;
Index: trunk/src/org/openstreetmap/josm/gui/mappaint/StyleKeys.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/mappaint/StyleKeys.java	(revision 5375)
+++ trunk/src/org/openstreetmap/josm/gui/mappaint/StyleKeys.java	(revision 5376)
@@ -11,4 +11,5 @@
     public static final String FILL_COLOR = "fill-color";
     public static final String FILL_IMAGE = "fill-image";
+    public static final String FILL_OPACITY = "fill-opacity";
     public static final String ICON_IMAGE = "icon-image";
     public static final String MODIFIER = "modifier";