Index: trunk/src/org/openstreetmap/josm/data/Preferences.java
===================================================================
--- trunk/src/org/openstreetmap/josm/data/Preferences.java	(revision 18903)
+++ trunk/src/org/openstreetmap/josm/data/Preferences.java	(revision 18907)
@@ -946,5 +946,5 @@
             }
         }
-        putListOfMaps("mappaint.style.entries", styleEntries);
+        putListOfMaps("mappaint.style.entries", styleEntries.isEmpty() ? null : styleEntries);
     }