Index: plugins/utilsplugin2/src/org/openstreetmap/josm/plugins/utilsplugin2/actions/SplitObjectAction.java
===================================================================
--- plugins/utilsplugin2/src/org/openstreetmap/josm/plugins/utilsplugin2/actions/SplitObjectAction.java	(revision 35924)
+++ plugins/utilsplugin2/src/org/openstreetmap/josm/plugins/utilsplugin2/actions/SplitObjectAction.java	(working copy)
@@ -572,8 +572,10 @@
             } else
                 return false;
         }
-        return (node == 2 || ways == 1 || ways == 2) || //only 2 nodes selected. one split-way selected. split-way + way to split.
-               (multipolygons == 1 && ways == 1);
+        // When splitting closed ways: only 2 nodes selected. one split-way selected. split-way + way to split.
+        // When splitting multipolygons: 1 multipolygon + 1 split way
+        return ((multipolygons == 0) && (node == 2 || ways == 1 || ways == 2)) ||
+               ((multipolygons == 1) && (ways == 1));
     }
 
     @Override